Vektorlayereigenschaften

Der Layereigenschaften Dialog für Vektorlayer enthält generelle Einstellungen, um das Aussehen der Layerobjekte in der Karte (Symbologie, Beschriftung, Diagramme) und die Interaktion mit der Maus (Aktionen, Kartentipps, form design) zu verwalten. Es bietet auch Informationen über die Layer.

To access the Layer Properties dialog:

  • In the Layers panel, double-click the layer or right-click and select Properties… from the pop-up menu;
  • Go to Layer ‣ Properties… menu when the layer is selected.

The vector Layer Properties dialog provides the following sections:

Tipp

Share full or partial properties of the layer styles

The Style menu at the bottom of the dialog allows you to import or export these or part of these properties from/to several destination (file, clipboard, database). See Managing Custom Styles.

Bemerkung

Because properties (symbology, label, actions, default values, forms…) of embedded layers (see Layer/Gruppen einbinden) are pulled from the original project file and to avoid changes that may break this behavior, the layer properties dialog is made unavailable for these layers.

Information Properties

metadata The Information tab is read-only and represents an interesting place to quickly grab summarized information and metadata on the current layer. Provided information are:

  • based on the provider of the layer (format of storage, path, geometry type, data source encoding, extent…);
  • picked from the filled metadata (access, links, contacts, history…);
  • or related to its geometry (spatial extent, CRS…) or its attributes (number of fields, characteristics of each…).

Source Properties

system Use this tab to define general settings for the vector layer.

../../../_images/vector_source_menu.png

Source tab in vector Layer Properties dialog

Other than setting the Layer name to display in the Layers Panel, available options include:

Koordinatenbezugssystem

  • Displays the layer’s Coordinate Reference System (CRS) as a PROJ.4 string. You can change the layer’s CRS, selecting a recently used one in the drop-down list or clicking on setProjection Select CRS button (see Coordinate Reference System Selector). Use this process only if the CRS applied to the layer is a wrong one or if none was applied. If you wish to reproject your data into another CRS, rather use layer reprojection algorithms from Processing or Save it into another layer.
  • Create spatial index (only for OGR-supported formats).
  • Update extents information for a layer.

Abfrageeditor

The Query Builder dialog is accessible through the eponym button at the bottom of the Source tab in the Layer Properties dialog, under the Provider feature filter group.

The Query Builder provides an interface that allows you to define a subset of the features in the layer using a SQL-like WHERE clause and to display the result in the main window. As long as the query is active, only the features corresponding to its result are available in the project.

You can use one or more layer attributes to define the filter in the Query Builder. The use of more than one attribute is shown in Figure_vector_querybuilder. In the example, the filter combines the attributes

  • toa (DateTime field: cast("toa" as character) > '2017-05-17' and cast("toa" as character) < '2019-12-24T18:00:00'),
  • name (String field: "name" > 'S') and
  • FID (Integer field: FID > 10)

using the AND, OR and NOT operators and parenthesis. This syntax (including the DateTime format for the toa field) works for GeoPackage datasets.

The filter is made at the data provider (OGR, PostgreSQL, MSSQL…) level. So the syntax depends on the data provider (DateTime is for instance not supported for the ESRI Shapefile format). The complete expression:

cast("toa" as character) > '2017-05-17' AND
cast("toa" as character) < '2019-12-24T18:00:00' AND
NOT ("name" > 'S' OR FID > 10)
../../../_images/queryBuilder.png

Abfrageeditor

You can also open the Query Builder dialog using the Filter… option from the Layer menu or the layer contextual menu. The Fields, Values and Operators sections in the dialog help you to construct the SQL-like query exposed in the Provider specific filter expression box.

The Fields list contains all the fields of the layer. To add an attribute column to the SQL WHERE clause field, double-click its name or just type it into the SQL box.

The Values frame lists the values of the currently selected field. To list all unique values of a field, click the All button. To instead list the first 25 unique values of the column, click the Sample button. To add a value to the SQL WHERE clause field, double click its name in the Values list. You can use the search box at the top of the Values frame to easily browse and find attribute values in the list.

The Operators section contains all usable operators. To add an operator to the SQL WHERE clause field, click the appropriate button. Relational operators ( = , > , …), string comparison operator (LIKE), and logical operators (AND, OR, …) are available.

The Test button helps you check your query and displays a message box with the number of features satisfying the current query. Use the Clear button to wipe the SQL query and revert the layer to its original state (ie, fully load all the features).

When a filter is applied, QGIS treats the resulting subset acts as if it were the entire layer. For example if you applied the filter above for ‚Borough‘ ("TYPE_2" = 'Borough'), you can not display, query, save or edit Anchorage, because that is a ‚Municipality‘ and therefore not part of the subset.

Tipp

Filtered layers are indicated in the Layers Panel

In the Layers panel, filtered layer is listed with a indicatorFilter Filter icon next to it indicating the query used when the mouse hovers over the button. Double-click the icon opens the Query Builder dialog for edit.

Symbology Properties

symbology The Symbology tab provides you with a comprehensive tool for rendering and symbolizing your vector data. You can use tools that are common to all vector data, as well as special symbolizing tools that were designed for the different kinds of vector data. However all types share the following dialog structure: in the upper part, you have a widget that helps you prepare the classification and the symbol to use for features and at the bottom the Layerdarstellung widget.

Tipp

Wechseln Sie schnell zwischen verschiedenen Layerdarstellungen

Using the Styles ‣ Add menu at the bottom of the Layer Properties dialog, you can save as many styles as needed. A style is the combination of all properties of a layer (such as symbology, labeling, diagram, fields form, actions…) as you want. Then, simply switch between styles from the context menu of the layer in Layers Panel to automatically get different representations of your data.

Tipp

Symbologie exportierten

Sie haben die Option die Vektorsymbologie von QGIS nach Google *.kml, *.dxf und MapInfo .*.tab Dateien zu exportieren. Öffnen Sie einfach das Rechte-Maustasten-Menü des Layers und klicken Sie auf Speichern als … ` um den Namen der Ausgabedatei und ihr Format festzulegen. Verwenden Sie im Dialog das :guilabel:`Darstellungsexport Menü um die Symbologie entweder als Objektdarstellung ‣ oder Symbollayerdarstellung ‣ zu speichern. Wenn Sie Symbollayer verwendet haben wird empfohlen die zweite Einstellung zu benutzen.

Objekt Darstellung

The renderer is responsible for drawing a feature together with the correct symbol. Regardless layer geometry type, there are four common types of renderers: single symbol, categorized, graduated and rule-based. For point layers, there are a point displacement and a heatmap renderers available while polygon layers can also be rendered with the inverted polygons and 2.5 D renderers.

Es gibt keinen kontinuirliche Farbe Renderer da es in der Tat einfach ein spezieller Fall des Abgestuft Renderers ist. Die Kategorisiert und Abgestuft Renderer können erstellt werden indem ein Symbol und ein Farbverlauf festgelegt werden - Sie werden die Farben für Symbole angemessen einsetzen. Für jeden Datentyp (Punkte, Linien und Polygone) sind Symbollayertypen erhältlich. Abhängig vom ausgesuchten Renderer gibt es verschiedene zusätzliche Bereiche.

Bemerkung

Wenn Sie den Darstellungstyp beim Einstellen des Stils eines Vektorlayers ändern werden die Einstellungen für das Symbol beibehalten. Beachten Sie dass dieses Vorgehen nur für eine Änderunge funktioniert. Wenn Sie den Darstellungstyp wiederholt ändern gehen die Einstellungen für das Symbol verloren.

Einzelsymbol Darstellung

The singleSymbol Single Symbol renderer is used to render all features of the layer using a single user-defined symbol. See Die Symbolauswahl for further information about symbol representation.

../../../_images/singlesymbol_ng_line.png

Linieneigenschaften Einzelsymbol

Tipp

Edit symbol directly from layer panel

If in your Layers Panel you have layers with categories defined through categorized, graduated or rule-based symbology mode, you can quickly change the fill color of the symbol of the categories by right-clicking on a category and choose the color you prefer from a colorWheel color wheel menu. Right-clicking on a category will also give you access to the options Hide all items, Show all items and Edit symbol.

No Symbols Renderer

The nullSymbol No Symbols renderer is a special use case of the Single Symbol renderer as it applies the same rendering to all features. Using this renderer, no symbol will be drawn for features, but labeling, diagrams and other non-symbol parts will still be shown.

Selections can still be made on the layer in the canvas and selected features will be rendered with a default symbol. Features being edited will also be shown.

This is intended as a handy shortcut for layers which you only want to show labels or diagrams for, and avoids the need to render symbols with totally transparent fill/border to achieve this.

Kategorisierte Darstellung

The categorizedSymbol Categorized renderer is used to render the features of a layer, using a user-defined symbol whose aspect reflects the discrete values of a field or an expression. The Categorized menu allows you to

  • select an existing field (using the Column listbox) or

  • type or build an expression using the expression Set column expression. The expression used to classify features can be of any type; it can for example:

    • be a comparison, e.g. myfield >= 100, $id = @atlas_featureid, myfield % 2 = 0, within( $geometry, @atlas_geometry ). In this case, QGIS returns values 1 (True) and 0 (False).

    • combine different fields, e.g. concat( field1, ' ', field2 ) particularly useful when you want to process classification on two or more fields simultaneously.

    • be a calculation on fields, e.g. myfield % 2, year( myfield ) field_1 + field_2.

    • be used to transform linear values in discrete classes, e.g.:

      CASE WHEN x > 1000 THEN 'Big' ELSE 'Small' END
      
    • combine several discrete values in one single category, e.g.:

      CASE
      WHEN building IN ('residence', 'mobile home') THEN 'residential'
      WHEN building IN ('commercial', 'industrial') THEN 'Commercial and Industrial'
      END
      

    Bemerkung

    While you can use any kind of expression to categorize features, for some complex expressions it might be simpler to use rule-based rendering.

  • the symbol (using the Die Symbolauswahl dialog) which will be used as base symbol for each class;

  • the range of colors (using the Color ramp listbox) from which color applied to the symbol is selected.

Then click on Classify button to create classes from the distinct value of the attribute column. Each class can be disabled unchecking the checkbox at the left of the class name.

Sie können das Symbol, den Wert oder die Beschriftung verändern, klicken Sie einfach auf das Element, das Sie ändern wollen.

Ein Rechtsklick zeigt ein Kontextmenü für Kopieren/Einfügen, Farbe ändern, Transparenz ändern, Ausgabeeinheit ändern, Breite ändern.

The example in figure_categorized_symbology shows the category rendering dialog used for the rivers layer of the QGIS sample dataset.

../../../_images/categorysymbol_ng_line.png

Kategorisierte Symbolisierungsoptionen

Tipp

Auswahl und Ändern von Mehrfachsymbolen

Mit der Symbologie können Sie Mehrfachsymbole auswählen und Rechtsklicken um Farbe, Transparenz, Größe oder Breite der ausgewählten Einträge zu ändern.

Tipp

Kategorien Symbolnamen zuordnen

Im Menü [Erweitert] unter den Klassen, können Sie eine der beiden Aktionen wählen, um Symbolnamen auf einen entsprechenden Kategorienamen in Ihrer Klassifizierung aufeinander abzustimmen. Matched to saved symbols Kategorienamen auf einen Symbolnamen aus Ihrem Stilmanager anpassen. Match to symbols from file Kategorienamen auf Symbolnamen von einer externen Datei anpassen.

Abgestufte Darstellung

The graduatedSymbol Graduated renderer is used to render all the features from a layer, using an user-defined symbol whose color or size reflects the assignment of a selected feature’s attribute to a class.

Like the Categorized Renderer, the Graduated Renderer allows you to define rotation and size scale from specified columns.

Genauso können Sie -analog zum Kategorisierten Renderer - im Menü auswählen:

  • The attribute (using the Column listbox or the expression Set column expression function)
  • Das Symbol (nutzen des Symbolauswahl Dialogs)
  • Die Legendenformatierung und die Genauigkeit
  • Die Methode, um das Symbol zu ändern: Farbe oder Größe
  • Die Farben (indem man die Farbverlaufsliste verwendet), wenn die Farbmethode ausgewählt ist
  • The size (using the size domain and its unit)

Then you can use the Histogram tab which shows an interactive histogram of the values from the assigned field or expression. Class breaks can be moved or added using the histogram widget.

Bemerkung

Sie können die statistische Zusammenfassung nutzen, um mehr Informationen über Ihren Vektorlayer zu erhalten. Siehe Statistical Summary Panel.

Zurück zu dem Klassen Reiter, Sie können die Anzahl der Klassen und auch den Modus für das Klassifizieren von Objekten innerhalb der Klassen (indem man die Modus-Liste verwendet) einstellen. Die möglichen Modi sind:

  • Equal Interval: each class has the same size (e.g. values from 0 to 16 and 4 classes, each class has a size of 4).
  • Quantile: each class will have the same number of element inside (the idea of a boxplot).
  • Natural Breaks (Jenks): the variance within each class is minimal while the variance between classes is maximal.
  • Standard Deviation: classes are built depending on the standard deviation of the values.
  • Schöne Unterbrechungen: Berechnet eine Sequenz von etwa n+1 mit gleichem Abstand, die den Bereich der Werte in x decken. Die Werte sind so gewählt, dass sie 1, 2 oder 5 mal einer Potenz von 10 sind .(basiert ziemlich auf der R statistischen Umgebung http://astrostatistics.psu.edu/datasets/R/html/base/html/pretty.html)

The listbox in the center part of the Symbology tab lists the classes together with their ranges, labels and symbols that will be rendered.

Klicken Sie auf den Klassifizieren Knopf um Klassen anhand des ausgewählten Modus zu erstellen. Jede Klasse kann anhand des Deaktivierens des Kontrollkästchens links neben dem Klassennamen ausgeschaltet werden.

Sie können das Symbol, den Wert oder die Beschriftung verändern, klicken Sie einfach auf das Element, das Sie ändern wollen.

Ein Rechtsklick zeigt ein Kontextmenü für Kopieren/Einfügen, Farbe ändern, Transparenz ändern, Ausgabeeinheit ändern, Breite ändern.

The example in figure_graduated_symbology shows the graduated rendering dialog for the rivers layer of the QGIS sample dataset.

../../../_images/graduatedsymbol_ng_line.png

Abgestufte Symbolisierungsoptionen

Tipp

Thematische Karten anhand von Ausdrücken erstellen

Categorized and graduated thematic maps can be created using the result of an expression. In the properties dialog for vector layers, the attribute chooser is extended with a expression Set column expression function. So you don’t need to write the classification attribute to a new column in your attribute table if you want the classification attribute to be a composite of multiple fields, or a formula of some sort.

Proportionale Symbole und mehrdimensionale Analysen

Proportional Symbol and Multivariate Analysis are not rendering types available from the Symbology rendering drop-down list. However with the data-defined override options applied over any of the previous rendering options, QGIS allows you to display your point and line data with such representation.

Proportionale Symbole erstellen

To apply a proportional rendering:

  1. First apply to the layer the single symbol renderer.

  2. Then set the symbol to apply to the features.

  3. Select the item at the upper level of the symbol tree, and use the dataDefined Data-defined override button next to the Size (for point layer) or Width (for line layer) option.

  4. Select a field or enter an expression, and for each feature, QGIS will apply the output value to the property and proportionally resize the symbol in the map canvas.

    If need be, use the Size assistant… option of the dataDefined menu to apply some transformation (exponential, flannery…) to the symbol size rescaling (see Using the data-defined assistant interface for more details).

You can choose to display the proportional symbols in the Layers panel and the print layout legend item: unfold the Advanced drop-down list at the bottom of the main dialog of the Symbology tab and select Data-defined size legend… to configure the legend items (see Data-defined size legend for details).

../../../_images/proportional_symbols.png

Scaling airports size based on elevation of the airport

Mehrdimensionale Analyse erzeugen

Eine mehrdimensionale Analyse hilft Ihnen, die Beziehungen zwischen zwei oder mehr Variablen auszuwerten z. B. kann eine als Farbverlauf und die andere als Größe dargestellt werden.

The simplest way to create multivariate analysis in QGIS is to:

  1. First apply a categorized or graduated rendering on a layer, using the same type of symbol for all the classes.
  2. Then, apply a proportional symbology on the classes:
    1. Click on the Change button above the classification frame: you get the Die Symbolauswahl dialog.
    2. Rescale the size or width of the symbol layer using the dataDefined data defined override widget as seen above.

Like the proportional symbol, the scaled symbology can be added to the layer tree, on top of the categorized or graduated classes symbols using the data defined size legend feature. And both representation are also available in the print layout legend item.

../../../_images/multivariate_example.png

Multivariate example with scaled size legend

Rule-based Renderer

The ruleBasedSymbol Rule-based renderer is used to render all the features from a layer, using rule-based symbols whose aspect reflects the assignment of a selected feature’s attribute to a class. The rules are based on SQL statements and can be nested. The dialog allows rule grouping by filter or scale, and you can decide if you want to enable symbol levels or use only the first-matched rule.

To create a rule:

  1. Activate an existing row by double-clicking it (by default, QGIS adds a symbol without a rule when the rendering mode is enabled) or click the projectProperties Edit rule or signPlus Add rule button.
  2. In the Edit Rule dialog that opens, you can define a label to help you identify each rule. This is the label that will be displayed in the Layers Panel and also in the print composer legend.
  3. Manually enter an expression in the text box next to the radioButtonOn Filter option or press the expression button next to it to open the expression string builder dialog.
  4. Use the provided functions and the layer attributes to build an expression to filter the features you’d like to retrieve. Press the Test button to check the result of the query.
  5. You can enter a longer label to complete the rule description.
  6. You can use the checkbox Scale Range option to set scales at which the rule should be applied.
  7. Finally, configure the symbol to use for these features.
  8. And press OK.

A new row summarizing the rule is added to the Layer Properties dialog. You can create as many rules as necessary following the steps above or copy pasting an existing rule. Drag-and-drop the rules on top of each other to nest them and refine the upper rule features in subclasses.

Selecting a rule, you can also organize its features in subclasses using the Refine selected rules drop-down menu. Automated rule refinement can be based on:

Refined classes appear like sub-items of the rule, in a tree hierarchy and like above, you can set symbology of each class.

In the Edit rule dialog, you can avoid writing all the rules and make use of the radioButtonOff Else option to catch all the features that do not match any of the other rules, at the same level. This can also be achieved by writing Else in the Rule column of the Layer Properties ‣ Symbology ‣ Rule-based dialog.

The created rules also appear in a tree hierarchy in the map legend. Double-click the rules in the map legend and the Symbology tab of the layer properties appears showing the rule that is the background for the symbol in the tree.

The example in figure_rule_based_symbology shows the rule-based rendering dialog for the rivers layer of the QGIS sample dataset.

../../../_images/rulesymbol_ng_line.png

Regelbasierte Symbolisierungsoptionen

Point displacement Renderer

The pointDisplacementSymbol Point Displacement renderer works to visualize all features of a point layer, even if they have the same location. To do this, the renderer takes the points falling in a given Distance tolerance from each other and places them around their barycenter following different Placement methods:

  • Ring: places all the features on a circle whose radius depends on the number of features to display.
  • Concentric rings: uses a set of concentric circles to show the features.
  • Grid: generates a regular grid with a point symbol at each intersection.

The Center symbol widget helps you customize the symbol and color of the middle point. For the distributed points symbols, you can apply any of the No symbols, Single symbol, Categorized, Graduated or Rule-based renderer using the Renderer drop-down list and customize them using the Renderer Settings… button.

While the minimal spacing of the Displacement lines depends on the point symbol renderer’s, you can still customize some of its settings such as the Stroke width, Stroke color and Size adjustment (eg, to add more spacing between the rendered points).

Use the Labels group options to perform points labeling: the labels are placed near the displaced position of the symbol, and not at the feature real position. Other than the Label attribute, Label font and Label color, you can set the Minimum map scale to display the labels.

../../../_images/poi_displacement.png

Dialog Punktverdrängung

Bemerkung

Point Displacement renderer does not alter feature geometry, meaning that points are not moved from their position. They are still located at their initial place. Changes are only visual, for rendering purpose. Use instead the Processing Points displacement algorithm if you want to create displaced features.

Point Cluster Renderer

Unlike the pointDisplacementSymbol Point Displacement renderer which blows up nearest or overlaid point features placement, the pointClusterSymbol Point Cluster renderer groups nearby points into a single rendered marker symbol. Based on a specified Distance, points that fall within from each others are merged into a single symbol. Points aggregation is made based on the closest group being formed, rather than just assigning them the first group within the search distance.

From the main dialog, you can:

  • set the symbol to represent the point cluster in the Cluster symbol; the default rendering displays the number of aggregated features thanks to the @cluster_size variable on Font marker symbol layer.
  • use the Renderer drop-down list to apply any of the other feature rendering types to the layer (single, categorized, rule-based…). Then, push the Renderer Settings… button to configure features‘ symbology as usual. Note that this renderer is only visible on features that are not clustered. Also, when the symbol color is the same for all the point features inside a cluster, that color sets the @cluster_color variable of the cluster.
../../../_images/cluster_symbol.png

Point Cluster dialog

Bemerkung

Point Cluster renderer does not alter feature geometry, meaning that points are not moved from their position. They are still located at their initial place. Changes are only visual, for rendering purpose. Use instead the Processing K-means clustering or DBSCAN clustering algorithm if you want to create cluster-based features.

Inverted Polygon Renderer

The invertedSymbol Inverted Polygon renderer allows user to define a symbol to fill in outside of the layer’s polygons. As above you can select subrenderers, namely Single symbol, Graduated, Categorized, Rule-Based or 2.5D renderer.

../../../_images/inverted_polygon_symbol.png

Umgekehrte Polygone Dialog

Heatmap Renderer

With the heatmapSymbol Heatmap renderer you can create live dynamic heatmaps for (multi)point layers. You can specify the heatmap radius in millimeters, points, pixels, map units or inches, choose and edit a color ramp for the heatmap style and use a slider for selecting a trade-off between render speed and quality. You can also define a maximum value limit and give a weight to points using a field or an expression. When adding or removing a feature the heatmap renderer updates the heatmap style automatically.

../../../_images/heatmap_symbol.png

Der Heatmap-Erweiterung Dialog

2.5D Renderer

Using the 25dSymbol 2.5D renderer it’s possible to create a 2.5D effect on your layer’s features. You start by choosing a Height value (in map units). For that you can use a fixed value, one of your layer’s fields, or an expression. You also need to choose an Angle (in degrees) to recreate the viewer position (0° means west, growing in counter clock wise). Use advanced configuration options to set the Roof Color and Wall Color. If you would like to simulate solar radiation on the features walls, make sure to check the checkbox Shade walls based on aspect option. You can also simulate a shadow by setting a Color and Size (in map units).

../../../_images/2_5dsymbol.png

2.5D dialog

Tipp

Using 2.5D effect with other renderers

Once you have finished setting the basic style on the 2.5D renderer, you can convert this to another renderer (single, categorized, graduated). The 2.5D effects will be kept and all other renderer specific options will be available for you to fine tune them (this way you can have for example categorized symbols with a nice 2.5D representation or add some extra styling to your 2.5D symbols). To make sure that the shadow and the „building“ itself do not interfere with other nearby features, you may need to enable Symbols Levels ( Advanced ‣ Symbol levels…). The 2.5D height and angle values are saved in the layer’s variables, so you can edit it afterwards in the variables tab of the layer’s properties dialog.

Layerdarstellung

From the Symbology tab, you can also set some options that invariably act on all features of the layer:

  • Opacity slider: You can make the underlying layer in the map canvas visible with this tool. Use the slider to adapt the visibility of your vector layer to your needs. You can also make a precise definition of the percentage of visibility in the menu beside the slider.

  • Blending mode at the Layer and Feature levels: You can achieve special rendering effects with these tools that you may previously only know from graphics programs. The pixels of your overlaying and underlaying layers are mixed through the settings described in Mischmodi.

  • Wenden Sie Zeicheneffekte auf alle Layerobjekte an, mit dem Zeicheneffekte Knopf.

  • Control feature rendering order allows you, using features attributes, to define the z-order in which they shall be rendered. Activate the checkbox and click on the sort button beside. You then get the Define Order dialog in which you:

    1. Choose a field or build an expression to apply to the layer features.
    2. Set in which order the fetched features should be sorted, i.e. if you choose Ascending order, the features with lower value are rendered under those with higher value.
    3. Define when features returning NULL value should be rendered: first (bottom) or last (top).
    4. Repeat the above steps as many times as rules you wish to use.

    The first rule is applied to all the features in the layer, z-ordering them according to their returned value. Then, within each group of features with the same value (including those with NULL value) and thus the same z-level, the next rule is applied to sort them. And so on…

../../../_images/layer_rendering_options.png

Layerdarstellungsoptionen

Andere Einstellungen

Symbol levels

Für Renderer, die Symbollayer gestapelt ermöglichen (nur Heatmap nicht) gibt es eine Option, um die Darstellungsreihenfolge der einzelnen Symbolebenen zu steuern.

For most of the renderers, you can access the Symbols levels option by clicking the Advanced button below the saved symbols list and choosing Symbol levels. For the Rule-based Renderer the option is directly available through Symbols Levels… button, while for Point displacement Renderer renderer the same button is inside the Rendering settings dialog.

Um die Symbolebenen zu aktivieren, wählen Sie checkbox Symbolebenen aktivieren. Jede Reihe zeigt eine kleine Vorschau des kombinierten Symbols, seiner Beschriftung und die individuellen Symbollayer, unterteilt in verschiedene Spalten mit einer Nummer. Die Nummern zeigen die Darstellungsreihenfolge, in der die Symbollayer gezeichnet werden. Niedrige Werteebenen werden zuerst gezeichnet, liegen ganz unten, während höhere Werte als letztes gezeichnet werden und über den anderen liegen.

../../../_images/symbol_levels.png

Symbolebenen Dialog

Bemerkung

Wenn Symbolebenen deaktiviert werden, werden alle Symbole entsprechend ihren jeweiligen Objektreihenfolge gezeichnet. Überlappende Symbole werden einfach zu anderen darunter verschleiert. Außerdem „verschmelzen“ ähnliche Symbole nicht mit anderen.

../../../_images/symbol_levels_examples.png

Unterschied von aktivierten (A) und deaktivierten (B) Symbolebenen

Data-defined size legend

When a layer is rendered with the proportional symbol or the multivariate rendering or when a scaled size diagram is applied to the layer, you can allow the display of the scaled symbols in both the Layers panel and the print layout legend.

To enable the Data-defined Size Legend dialog to render symbology, select the eponym option in the Advanced button below the saved symbols list. For diagrams, the option is available under the Legend tab. The dialog provides the following options to:

  • select the type of legend: radioButtonOn Legend not enabled, radioButtonOff Separated legend items and radioButtonOff Collapsed legend. For the latter option, you can select whether the legend items are aligned at the Bottom or at the Center;
  • set the symbol to use for legend representation;
  • insert the title in the legend;
  • resize the classes to use: by default, QGIS provides you with a legend of five classes (based on natural pretty breaks) but you can apply your own classification using the checkbox Manual size classes option. Use the signPlus and signMinus buttons to set your custom classes values and labels.

A preview of the legend is displayed in the right panel of the dialog and updated as you set the parameters. For collapsed legend, a leader line from the horizontal center of the symbol to the corresponding legend text is drawn.

../../../_images/data_defined_size_legend.png

Setting size scaled legend

Bemerkung

Currently, data-defined size legend for layer symbology can only be applied to point layer using single, categorized or graduated symbology.

Zeicheneffekte

Damit die Layerdarstellung verbessert und vermieden (oder zumindest reduziert) wird, dass andere Software auf die endgültige Darstellung der Karte umsortiert, bietet QGIS eine weitere leistungsfähige Funktionalität: Die Option paintEffects Zeicheneffekte, die zur Anpassung Zeicheneffekte für die Visualisierung von Vektorlayern hinzufügt.

The option is available in the Layer Properties ‣ Symbology dialog, under the Layer rendering group (applying to the whole layer) or in symbol layer properties (applying to corresponding features). You can combine both usage.

Paint effects can be activated by checking the checkbox Draw effects option and clicking the paintEffects Customize effects button. That will open the Effect Properties Dialog (see figure_effects_source). The following effect types, with custom options are available:

  • Source: Draws the feature’s original style according to the configuration of the layer’s properties. The Opacity of its style can be adjusted as well as the Blend mode and Draw mode. These are common properties for all types of effects.

    ../../../_images/source.png

    Zeicheneffekte: Dialog Quelle

  • Blur: Adds a blur effect on the vector layer. The custom options that you can change are the Blur type (Stack blur (fast) or Gaussian blur (quality)) and the Blur strength.

    ../../../_images/blur.png

    Zeicheneffekte: Dialog verwischen

  • Colorise: This effect can be used to make a version of the style using one single hue. The base will always be a grayscale version of the symbol and you can:

    • Use the selectString Grayscale to select how to create it: options are ‚By lightness‘, ‚By luminosity‘, ‚By average‘ and ‚Off‘.
    • If checkbox Colorise is selected, it will be possible to mix another color and choose how strong it should be.
    • Control the Brightness, Contrast and Saturation levels of the resulting symbol.
    ../../../_images/colorise.png

    Zeicheneffekte: Dialog einfärben

  • Drop Shadow: Using this effect adds a shadow on the feature, which looks like adding an extra dimension. This effect can be customized by changing the Offset angle and distance, determining where the shadow shifts towards to and the proximity to the source object. Drop Shadow also has the option to change the Blur radius and the Color of the effect.

    ../../../_images/drop_shadow.png

    Zeicheneffekte: Dialog Schattenwurf

  • Inner Shadow: This effect is similar to the Drop Shadow effect, but it adds the shadow effect on the inside of the edges of the feature. The available options for customization are the same as the Drop Shadow effect.

    ../../../_images/inner_shadow.png

    Zeicheneffekte: Dialog Innerer Schatten

  • Inner Glow: Adds a glow effect inside the feature. This effect can be customized by adjusting the Spread (width) of the glow, or the Blur radius. The latter specifies the proximity from the edge of the feature where you want any blurring to happen. Additionally, there are options to customize the color of the glow using a Single color or a Color ramp.

    ../../../_images/inner_glow.png

    Zeicheneffekte: Dialog Inneres Glühen

  • Outer Glow: This effect is similar to the Inner Glow effect, but it adds the glow effect on the outside of the edges of the feature. The available options for customization are the same as the Inner Glow effect.

    ../../../_images/outer_glow.png

    Zeicheneffekte: Dialog Äußeres Glühen

  • Transform: Adds the possibility of transforming the shape of the symbol. The first options available for customization are the Reflect horizontal and Reflect vertical, which actually create a reflection on the horizontal and/or vertical axes. The other options are:

    • Shear X,Y: Slants the feature along the X and/or Y axis.
    • Scale X,Y: Enlarges or minimizes the feature along the X and/or Y axis by the given percentage.
    • Rotation: Turns the feature around its center point.
    • and Translate X,Y changes the position of the item based on a distance given on the X and/or Y axis.
    ../../../_images/transform.png

    Zeicheneffekte: Dialog transformieren

One or more effect types can be used at the same time. You (de)activate an effect using its checkbox in the effects list. You can change the selected effect type by using the selectString Effect type option. You can reorder the effects using arrowUp Move up and arrowDown Move down buttons, and also add/remove effects using the signPlus Add new effect and signMinus Remove effect buttons.

There are some common options available for all draw effect types. Opacity and Blend mode options work similar to the ones described in Layerdarstellung and can be used in all draw effects except for the transform one.

There is also a selectString Draw mode option available for every effect, and you can choose whether to render and/or modify the symbol, following some rules:

  • Effects render from top to bottom.
  • Render only mode means that the effect will be visible.
  • Modifier only mode means that the effect will not be visible but the changes that it applies will be passed to the next effect (the one immediately below).
  • The Render and Modify mode will make the effect visible and pass any changes to the next effect. If the effect is at the top of the effects list or if the immediately above effect is not in modify mode, then it will use the original source symbol from the layers properties (similar to source).

Labels Properties

The labeling Labels properties provides you with all the needed and appropriate capabilities to configure smart labeling on vector layers. This dialog can also be accessed from the Layer Styling panel, or using the labeling Layer Labeling Options icon of the Labels toolbar.

The first step is to choose the labeling method from the drop-down list. Available methods are:

  • labelingNone No labels: the default value, showing no labels from the layer
  • labeling Single labels, described below
  • labelingRuleBased Rule-based labeling
  • and labelingObstacle Blocking: allows to set a layer as just an obstacle for other layer’s labels without rendering any labels of its own.

Setting a label

The next steps assume you select the labeling Single labels option, enabling following tabs that help you configure the labeling:

It also enables the Label with drop-down list, from which you can select an attribute column to use. Click expression if you want to define labels based on expressions - See Ausdrucksbasierte Beschriftungen definieren.

The following steps describe simple labeling without using the Data defined override functions, which are situated next to the drop-down menus - see Datendefinierte Übersteuerung für das Beschriften for a use case.

../../../_images/label_menu_text.png

Layer labeling settings - Text tab

Text tab

In the text Text tab, you can define the Font, Style, and Size of your labels‘ text (see Figure_labels). There are options available to set the labels‘ Color and Transparency. Use the Type case option to change the capitalization style of the text. You have the possibility to render the text as ‚All uppercase‘, ‚All lowercase‘ or ‚Capitalize first letter‘. In Spacing, you can change the space between words and between individual letters. Finally, use the Blend mode option to determine how your labels will mix with the map features below them (see more about it in Mischmodi).

The Apply label text substitutes option gives you ability to specify a list of texts to substitute to texts in feature labels (e.g., abbreviating street types). Replacement texts are thus used to display labels in the map canvas. Users can also export and import lists of substitutes to make reuse and sharing easier.

Formatting tab

In the labelformatting Formatting tab, you can define a character for a line break in the labels with the Wrap on character option. You can also format the Line Height and the alignment. For the latter, typical values are available (left, right, and center), plus Follow label placement for point layers. When set to this mode, text alignment for labels will be dependent on the final placement of the label relative to the point. E.g., if the label is placed to the left of the point, then the label will be right aligned, while if it is placed to the right, it will be left aligned.

For line vector layers you can include Line directions symbols to help determine the lines directions. They work particularly well when used with the curved or Parallel placement options from the Placement tab. There are options to set the symbols position, and to reverse direction.

Use the checkbox Formatted numbers option to format numeric labels. You can set the number of Decimal places. By default, 3 decimal places will be used. Use the checkbox Show plus sign if you want to show the plus sign in positive numbers.

Buffer tab

To create a buffer around the labels, activate the checkbox Draw text buffer checkbox in the labelbuffer Buffer tab. You can set the buffer’s Size, color, and Transparency. The buffer expands from the label’s outline , so, if the checkbox color buffer’s fill checkbox is activated, the buffer interior is filled. This may be relevant when using partially transparent labels or with non-normal blending modes, which will allow seeing behind the label’s text. Deactivating checkbox color buffer’s fill checkbox (while using totally transparent labels) will allow you to create outlined text labels.

Background tab

In the labelbackground Background tab, you can define with Size X and Size Y the shape of your background. Use Size type to insert an additional ‚Buffer‘ into your background. The buffer size is set by default here. The background then consists of the buffer plus the background in Size X and Size Y. You can set a Rotation where you can choose between ‚Sync with label‘, ‚Offset of label‘ and ‚Fixed‘. Using ‚Offset of label‘ and ‚Fixed‘, you can rotate the background. Define an Offset X,Y with X and Y values, and the background will be shifted. When applying Radius X,Y, the background gets rounded corners. Again, it is possible to mix the background with the underlying layers in the map canvas using the Blend mode (see Mischmodi).

Shadow tab

Use the labelshadow Shadow tab for a user-defined Draw drop shadow. The drawing of the background is very variable. Choose between ‚Lowest label component‘, ‚Text‘, ‚Buffer‘ and ‚Background‘. The Offset angle depends on the orientation of the label. If you choose the checkbox Use global shadow checkbox, then the zero point of the angle is always oriented to the north and doesn’t depend on the orientation of the label. You can influence the appearance of the shadow with the Blur radius. The higher the number, the softer the shadows. The appearance of the drop shadow can also be altered by choosing a blend mode.

Placement tab

Choose the labelplacement Placement tab for configuring label placement and labeling priority. Note that the placement options differ according to the type of vector layer, namely point, line or polygon, and are affected by the global PAL setting.

Platzierung für Punktlayer

With the radioButtonOn Cartographic placement mode, point labels are generated with a better visual relationship with the point feature, following ideal cartographic placement rules. Labels can be placed at a set Distance either from the point feature itself or from the bounds of the symbol used to represent the feature. The latter option is especially useful when the symbol size isn’t fixed, e.g. if it’s set by a data defined size or when using different symbols in a categorized renderer.

Standardmäßig sind die Platzierungen in dieser Reihenfolge festgelegt:

  1. oben rechts
  2. oben links
  3. unten rechts
  4. unten links
  5. mitte rechts
  6. mitte links
  7. oben, leicht rechts
  8. unten, leicht rechts

Placement priority can, however, be customized or set for an individual feature using a data defined list of prioritised positions. This also allows only certain placements to be used, so e.g. for coastal features you can prevent labels being placed over the land.

Die Einstellung radioButtonOn Um den Punkt platziert die Beschriftung in einem gleichen Kreisradius (einzustellen in Abstand) um das Objekt. Die Platzierung der Beschriftung kann auch eingeschränkt werden, in der Quadrant Option.

With the radioButtonOn Offset from point, labels are placed at a fixed offset from the point feature. You can select the Quadrant in which to place your label. You are also able to set the Offset X,Y distances between the points and their labels and can alter the angle of the label placement with the Rotation setting. Thus, placement in a selected quadrant with a defined rotation is possible.

Platzierung für Linienlayer

Label options for line layers include radioButtonOn Parallel, radioButtonOff Curved or radioButtonOff Horizontal. For the radioButtonOn Parallel and radioButtonOff Curved options, you can set the position to checkbox Above line, checkbox On line and checkbox Below line. It’s possible to select several options at once. In that case, QGIS will look for the optimal label position. For Parallel and curved placement options, you can also use the line orientation for the position of the label. Additionally, you can define a Maximum angle between curved characters when selecting the radioButtonOff Curved option (see Figure_labels_placement_line).

../../../_images/line_label_placement.png

Label placement examples in lines

For all three placement options, in Repeat, you can set up a minimum distance for repeating labels. The distance can be in mm or in map units.

Platzierung für Polygonlayer

You can choose one of the following options for placing labels in polygons (see figure_labels_placement_polygon):

  • radioButtonOn Offset from centroid,
  • radioButtonOff Horizontal (slow),
  • radioButtonOff Around centroid,
  • radioButtonOff Free (slow),
  • radioButtonOff Using perimeter,
  • and radioButtonOff Using perimeter (curved).

In the Offset from centroid settings you can specify if the centroid is of the radioButtonOn visible polygon or radioButtonOff whole polygon. That means that either the centroid is used for the polygon you can see on the map or the centroid is determined for the whole polygon, no matter if you can see the whole feature on the map. You can place your label within a specific quadrant, and define offset and rotation.

The Around centroid setting places the label at a specified distance around the centroid. Again, you can define radioButtonOn visible polygon or radioButtonOff whole polygon for the centroid.

With the Horizontal (slow) or Free (slow) options, QGIS places at the best position either a horizontal or a rotated label inside the polygon.

With the Using perimeter option, the label will be drawn next to the polygon boundary. The label will behave like the parallel option for lines. You can define a position and a distance for the label. For the position, checkbox Above line, checkbox On line, checkbox Below line and checkbox Line orientation dependent position are possible. You can specify the distance between the label and the polygon outline, as well as the repeat interval for the label.

The Using perimeter (curved) option helps you draw the label along the polygon boundary, using a curved labeling. In addition to the parameters available with Using perimeter setting, you can set the Maximum angle between curved characters polygon, either inside or outside.

../../../_images/polygon_label_placement.png

Label placement examples in polygons

In the priority section you can define the priority with which labels are rendered for all three vector layer types (point, line, polygon). This placement option interacts with the labels from other vector layers in the map canvas. If there are labels from different layers in the same location, the label with the higher priority will be displayed and the others will be left out.

Rendering tab

In the render Rendering tab, you can tune when the labels can be rendered and their interaction with other labels and features.

Unter den Beschriftungsoptionen finden Sie die skalierungsbasierte und die Pixelgrößenbasierte Sichtbarkeitseinstellungen.

Der Beschriftung Z-Index bestimmt, in welcher Reihenfolge, welche Beschriftung dargestellt wird, als auch in welcher Verbindung mit anderen Objekten in dem Layer (nutzen Sie datendefinierte Übersteuerung), wie mit Beschriftungen anderer Layer. Beschriftungen mit einem hohen Z-Index werden an oberster Stelle dargestellt.

Zusätzlich ist die Logik optimiert worden, so, dass wenn zwei Beschriftungen den selben Z-Index haben, dann:

  • wenn sie aus dem selben Layer sind, wird die kleinere Beschriftung über dem größeren gezeichnet
  • wenn sie aus verschiedenen Layer sind, werden die Beschriftungen in der selben Reihenfolge gezeichnet, wie die Layer an sich (d. h. unter Berücksichtigung der Reihenfolge in der Kartenlegende).

Beachten Sie, dass diese Einstellung Beschriftungen nicht unter andere Objekte anderer Layer zeichnet, es kontrolliert nur die Reihenfolge, in welcher Beschriftungen über allen Layerobjekten gezeichnet werden.

Während der Darstellung der Beschriftungen und um lesbare Beschriftungen anzuzeigen, wertet QGIS automatisch die Position der Beschriftungen aus und kann, im Falle einer Kollision, einige von ihnen verstecken. Trotzdem können Sie checkbox Alle Beschriftungen für diesen layer anzeigen (including colliding labels) wählen und Ihre Kollisionen manuell beheben.

Mit datendefinierten Ausdrücken in Beschriftungen anzeigen and Immer anzeigen können Sie Feineinstellungen vornehmen, welche Beschriftungen dargestellt werden.

Unter Objektoptionen können Sie Jeden Teil eines Multi-Polygons beschriften und Begrenze die Anzahl der zu beschriftenden Objekte wählen. Sowohl Linien- als auch Polygonlayer bieten die Möglichkeit eine Mindestgröße für das Beschriften einzustellen, wählen Sie Unterdrücke Beschriftungen für Objekte kleiner als. Für Polygonlayer können Sie auch einen Filter vornehmen, der Beschriftungen anzeigt, wenn sie komplett in dem Polygon liegen oder nicht. Für Linienlayer können Sie wählen Verschmelze verbundene Linien um doppelte Beschriftung zu vermeiden, um eine lebhafte Karte darzustellen in Verbindung mit dem Abstand oder Wiederholen Optionen im Reiter Platzierung.

In dem Hindernis Rahmen, können Sie die Abdeckungsbeziehungen zwischen Beschriftungen und Objekten bearbeiten. Aktivieren Sie die checkbox Discourage labels from covering features Option um zu entscheiden, ob Objekte des Layers als Hindernis für Beschriftung wirken soll (inklusive Beschriftungen anderer Objekte des selben Layers). Ein Hindernis ist ein Merkmal, QGIS versucht so weit wie möglich keine Beschriftungen übereinander zu platzieren. Anstatt des gesamten Layers, können Sie Teilmengen als Hindernis definieren, indem Sie dataDefined datendefinierte Übersteuerung verwenden.

Der slider Prioritätsschieberegler für Hindernisse erlaubt es Ihnen Beschriftungen von bestimmten Layern zum überlappen zu bevorzugen. Eine Geringe Gewichtung einer Hindernispriorität bedeutet, dass Objekte eines Layers weniger als Hindernis gelten und somit eher durch Beschriftungen überlagert werden. Die Priorität kann ebenso datendefiniert sein, so dass innerhalb des selben Layers, bestimmte Objekte wahrscheinlicher überdeckt werden als andere.

Für Polygonlayer können Sie dezArt von Hindernisobjekten wählen durch Minimierung der Beschriftungsplatzierung sein könnten:

  • over the feature’s interior: avoids placing labels over the interior of the polygon (prefers placing labels totally outside or just slightly inside the polygon)
  • or over the feature’s boundary: avoids placing labels over boundary of the polygon (prefers placing labels outside or completely inside the polygon). E.g., it can be useful for regional boundary layers, where the features cover an entire area. In this case, it’s impossible to avoid placing labels within these features, and it looks much better to avoid placing them over the boundaries between features.

Setting the automated placement engine

In the top right corner of the Labels tab, you can use the autoPlacement Automated placement settings (applies to all layers) to configure a global and automated behavior of the labels. Clicking the autoPlacement button provides you with the following options:

../../../_images/placement_engine.png

The labels automated placement engine

  • The Search method combobox provides you with different placement methods for finding good placement solutions for point, line and polygon labeling. More details in this article.
  • The Number of candidates controls set how many label placement candidates should be generated for each feature type. The more candidates generated, the better the labeling will be - but at a cost of rendering speed. Smaller number of candidates results in less labels placed but faster redraws.
  • checkbox Draw text as outlines: controls whether text labels are drawn (and exported) as either proper text objects OR as paths only. If they are exported as text objects then they can be edited in external applications (e.g. Inkscape) as normal text. BUT the side effect is that the rendering quality is decreased, AND there’s issues with rendering when certain text settings like buffers are in place. That’s why drawing as outlines is recommended. Note that when exporting a layout to svg there’s actually an override for this setting - so you can leave the project rendering as outlines but for a .svg export export the labels as text.
  • checkbox Show partial labels: controls whether labels which fall partially outside of the map extent should be rendered. If checked, these labels will be shown (when there’s no way to place them fully within the visible area). If unchecked then partial visible labels will be skipped.
  • checkbox show all labels for all layers (i.e. including colliding objects). Note that this option can be also set per layer (see Rendering tab)
  • checkbox show candidates (for debugging): controls whether boxes should be drawn on the map showing all the candidates generated for label placement. Like the label says, it’s useful only for debugging and testing the effect different labeling settings have. This could be handy for a better manual placement with tools from the label toolbar.

Regelbasierte Beschriftung

With rule-based labeling multiple label configurations can be defined and applied selectively on the base of expression filters and scale range, as in Rule-based rendering.

To create a rule, select the labelingRuleBased Rule-based labeling option in the main drop-down list from the Labels tab and click the signPlus button at the bottom of the dialog. Then fill the new dialog with a description and an expression to filter features. You can also set a scale range in which the label rule should be applied. The other options available in this dialog are the common settings seen beforehand.

../../../_images/label_rule_settings.png

Regeleigenschaften

A summary of existing rules is shown in the main dialog (see figure_labels_rule_based). You can add multiple rules, reorder or imbricate them with a drag-and-drop. You can as well remove them with the signMinus button or edit them with projectProperties button or a double-click.

../../../_images/label_rules_panel.png

Regelbasierte Beschriftung Bedienfelder

Ausdrucksbasierte Beschriftungen definieren

Whether you choose single or rule-based labeling type, QGIS allows using expressions to label features.

Assuming you are using the Single labels method, click the expression icon near the Label with drop-down list in the labeling Labels tab of the properties dialog.

In figure_labels_expression, you see a sample expression to label the alaska trees layer with tree type and area, based on the field ‚VEGDESC‘, some descriptive text, and the function $area in combination with format_number() to make it look nicer.

../../../_images/label_expression.png

Ausdrücke für das Beschriften verwenden

Expression based labeling is easy to work with. All you have to take care of is that:

  • You may need to combine all elements (strings, fields, and functions) with a string concatenation function such as concat, + or ||. Be aware that in some situations (when null or numeric value are involved) not all of these tools will fit your need.
  • Strings are written in ‚single quotes‘.
  • Fields are written in „double quotes“ or without any quote.

Schauen wir uns einige Beispiele an:

  1. Label based on two fields ‚name‘ and ‚place‘ with a comma as separator:

    "name" || ', ' || "place"
    

    Returns:

    John Smith, Paris
    
  2. Label based on two fields ‚name‘ and ‚place‘ with other texts:

    'My name is ' + "name" + 'and I live in ' + "place"
    'My name is ' || "name" || 'and I live in ' || "place"
    concat('My name is ', name, ' and I live in ', "place")
    

    Returns:

    My name is John Smith and I live in Paris
    
  3. Label based on two fields ‚name‘ and ‚place‘ with other texts combining different concatenation functions:

    concat('My name is ', name, ' and I live in ' || place)
    

    Returns:

    My name is John Smith and I live in Paris
    

    Or, if the field ‚place‘ is NULL, returns:

    My name is John Smith
    
  4. Multi-line label based on two fields ‚name‘ and ‚place‘ with a descriptive text:

    concat('My name is ', "name", '\n' , 'I live in ' , "place")
    

    Returns:

    My name is John Smith
    I live in Paris
    
  5. Label based on a field and the $area function to show the place’s name and its rounded area size in a converted unit:

    'The area of ' || "place" || ' has a size of '
    || round($area/10000) || ' ha'
    

    Returns:

    The area of Paris has a size of 10500 ha
    
  6. Create a CASE ELSE condition. If the population value in field population is <= 50000 it is a town, otherwise it is a city:

    concat('This place is a ',
    CASE WHEN "population" <= 50000 THEN 'town' ELSE 'city' END)
    

    Returns:

    This place is a town
    
  7. Display name for the cities and no label for the other features (for the „city“ context, see example above):

    CASE WHEN "population" > 50000 THEN "NAME" END
    

    Returns:

    Paris
    

Wie Sie im Ausdruckeditor sehen können stehen Ihnen hunderte von Funktionen zur Verfügung um einfache und sehr komplexe Ausdrücke zumBeschriften Ihrer Daten in QGIS zu erstellen. Siehe das Ausdrücke Kapitel für weitere Informationen und ein Beispiel zu Ausdrücken.

Datendefinierte Übersteuerung für das Beschriften

With the dataDefined Data defined override function, the settings for the labeling are overridden by entries in the attribute table or expressions based on them. This feature can be used to set values for most of the labeling options described above.

For example, using the Alaska QGIS sample dataset, let’s label the airports layer with their name, based on their militarian USE, i.e. whether the airport is accessible to :

  • military people, then display it in gray color, size 8;
  • others, then show in blue color, size 10.

To do this, after you enabled the labeling on the NAME field of the layer (see Setting a label):

  1. Activate the Text tab.

  2. Click on the dataDefined icon next to the Size property.

  3. Select Edit… and type:

    CASE
      WHEN "USE" like '%Military%' THEN 8 -- because compatible values are 'Military'
                                          -- and 'Joint Military/Civilian'
      ELSE 10
    END
    
  4. Press OK to validate. The dialog closes and the dataDefined button becomes dataDefineExpressionOn meaning that an rule is being run.

  5. Then click the button next to the color property, type the expression below and validate:

    CASE
      WHEN "USE" like '%Military%' THEN '150, 150, 150'
      ELSE '0, 0, 255'
    END
    

Likewise, you can customize any other property of the label, the way you want. See more details on the dataDefined Data-define override widget’s description and manipulation in Datendefinierte Übersteuerung Setup section.

../../../_images/label_attribute_data_defined.png

Airports labels are formatted based on their attributes

The Label Toolbar

The Label Toolbar provides some tools to manipulate labeling label or diagram diagram properties, but only if the corresponding data-defined option is indicated (otherwise, buttons are disabled). Layer might also need to be in edit mode.

../../../_images/diagram_toolbar.png

The Label toolbar

While for readability, label has been used below to describe the Label toolbar, note that when mentioned in their name, the tools work almost the same way with diagrams:

  • pinLabels Pin/Unpin Labels And Diagrams that has data-defined position. By clicking or draging an area, you pin label(s). If you click or drag an area holding Shift, label(s) are unpinned. Finally, you can also click or drag an area holding Ctrl to toggle the pin status of label(s).
  • showPinnedLabels Highlight Pinned Labels And Diagrams. If the vector layer of the label is editable, then the highlighting is green, otherwise it’s blue.
  • moveLabel Move Label And Diagram that has data-defined position. You just have to drag the label to the desired place.
  • showHideLabels Show/Hide Labels And Diagrams that has data-defined visbility. If you click or drag an area holding Shift, then label(s) are hidden. When a label is hidden, you just have to click or drag an area around the feature’s point to restore its visibility.
  • rotateLabel Rotate Label. Click the label and move around and you get the text rotated.
  • changeLabelProperties Change Label. It opens a dialog to change the clicked label properties; it can be the label itself, its coordinates, angle, font, size… as long as this property has been mapped to a field.

Warnung

Label tools overwrite current field values

Using the Label toolbar to customize the labeling actually writes the new value of the property in the mapped field. Hence, be careful to not inadvertently replace data you may need later!

Bemerkung

The Auxiliary Storage Properties mechanism may be used to customize labeling (position, and so on) without modifying the underlying data source.

Customize the labels from the map canvas

Combined with the Label Toolbar, the data defined override setting helps you manipulate labels in the map canvas (move, edit, rotate). We now describe an example using the data-defined override function for the moveLabelMove label function (see figure_labels_coordinate_data_defined).

  1. Importieren Sie lakes.shp aus dem QGIS Beispieldatensatz.

  2. Doppelklicken Sie den Layer um die Layereigenschaften zu öffnen. Klicken Sie auf Beschriftungen und Platzierung. Wählen Sie radioButtonOn Abstand vom Punkt.

  3. Look for the Data defined entries. Click the dataDefined icon to define the field type for the Coordinate. Choose xlabel for X and ylabel for Y. The icons are now highlighted in yellow.

    ../../../_images/label_coordinate_data_defined.png

    Das Beschriften von Polygonlayern mit datendefinierter Übersteuerung

  4. Zoomen Sie auf einen See.

  5. Set editable the layer using the toggleEditing Toggle Editing button.

  6. Go to the Label toolbar and click the moveLabel icon. Now you can shift the label manually to another position (see figure_labels_move). The new position of the label is saved in the xlabel and ylabel columns of the attribute table.

  7. Using The Geometry Generator with the expression below, you can also add a linestring symbol layer to connect each lake to its moved label:

    make_line( centroid( $geometry ), make_point( "xlabel", "ylabel" ) )
    
    ../../../_images/move_label.png

    Moved labels

Bemerkung

The Auxiliary Storage Properties mechanism may be used with data-defined properties without having an editable data source.

Diagrams Properties

diagram The Diagrams tab allows you to add a graphic overlay to a vector layer (see figure_diagrams_attributes).

Die aktuelle Kernimplementation von Diagrammen bietet Unterstützung von:

  • diagramNone No diagrams: the default value with no diagram displayed over the features;
  • piechart Pie charts, a circular statistical graphic divided into slices to illustrate numerical proportion. The arc length of each slice is proportional to the quantity it represents;
  • text Text diagrams, a horizontaly divided circle showing statistics values inside;
  • and histogram Histograms.

In the top right corner of the Diagrams tab, the autoPlacement Automated placement settings (applies to all layers) button provides means to control diagram labels placement on the map canvas.

Tipp

Switch quickly between types of diagrams

Given that the settings are almost common to the different types of diagram, when designing your diagram, you can easily change the diagram type and check which one is more appropriate to your data without any loss.

For each type of diagram, the properties are divided into several tabs:

Attribute

Attribute`definiert, welche Variablen in dem Diagramm gezeigt werden. Nutzen Sie den :sup:`Objekt hinzufügen Knopf um das gewünschte Feld in das ‚Zugeordnete Attribut‘ Bedienfeld zu schieben. Erzeugte Attribute mit den Ausdrücke können auch genutzt werden.

You can move up and down any row with click and drag, sorting how attributes are displayed. You can also change the label in the ‚Legend‘ column or the attribute color by double-clicking the item.

This label is the default text displayed in the legend of the print layout or of the layer tree.

../../../_images/diagram_tab.png

Diagram properties - Attributes tab

Rendering

Rendering defines how the diagram looks like. It provides general settings that do not interfere with the statistic values such as:

  • the graphic’s opacity, its outline width and color;
  • and, depending on the type of diagram:
    • the width of the bar in case of histogram;
    • the circle background color in case of text diagram, and the font used for texts;
    • die Ausrichtung der linken Linie von der ersten Scheibe im Tortendiagramm. Beachten Sie, die Scheiben werden im Uhrzeigersinn angezeigt.

In this tab, you can also manage and fine tune the diagram visibility with different options:

  • Diagram z-index: controls how diagrams are drawn on top of each other and on top of labels. A diagram with a high index is drawn over diagrams and labels;
  • checkbox Show all diagrams: shows all the diagrams even if they overlap each other;
  • Show diagram: allows only specific diagrams to be rendered;
  • Always Show: selects specific diagrams to always render, even when they overlap other diagrams or map labels;
  • setting the Scale dependent visibility;
  • Discourage diagrams and labels from covering features: defines features to use as obstacles, ie QGIS will try to not place diagrams nor labels over these features.
../../../_images/diagram_tab_appearance.png

Diagram properties - Rendering tab

Größe

Size is the main tab to set how the selected statistics are represented. The diagram size units can be ‚Millimeter‘, ‚Points‘, Pixels, ‚Map Units‘ or ‚Inches‘. You can use :

  • Feste Größe, eine feste Größe zum Darstellen der Grafik aller Objekte, außer beim Darstellen des Histogramms
  • oder Skalierte Größe, basiert auf einem Ausdruck, der Layerattribute benutzt.
../../../_images/diagram_tab_size.png

Diagram properties - Size tab

Platzierung

Platzierung hilft die Diagramm Position einzustellen. Entsprechend dem Layergeometrietyp, bietet es verschiedene Optionen zur Platzierung:

  • ‚Over the point‘ or ‚Around the point‘ for point geometry. The latter variable requires a radius to follow.
  • ‚Over the line‘ or ‚Around the line‘ for line geometry. Like point feature, the last variable requires a distance to respect and user can specify the diagram placement relative to the feature (‚above‘, ‚on‘ and/or ‚below‘ the line) It’s possible to select several options at once. In that case, QGIS will look for the optimal position of the diagram. Remember that here you can also use the line orientation for the position of the diagram.
  • ‚Über dem Zentrum‘, ‚Um das Zentrum‘ (mit eingestellter Distanz), ‚Umfang‘ und irgendwo ‚Innerhalb des Polygons‘ sind die Optionen für Polygonobjekte.

The diagram can also be placed using feature data to fill the coordinates X and Y fields.

The placement of the diagrams can interact with the labeling, so you can detect and solve position conflicts between diagrams and labels by setting the Priority slider value.

../../../_images/diagram_tab_placement.png

Vector properties dialog with diagram properties, Placement tab

Optionen

Der Reiter Optionen hat nur Einstellungen im Fall eines Histrogramms. Sie können wählen, ob die Orientierung der Leiste ‚oben‘, ‚unten‘, ‚rechts‘ und ‚links‘ ist.

Legend

From the Legend tab, you can choose to display items of the diagram in the Layerfenster, and in the print layout legend, next to the layer symbology:

  • check Show legend entries for diagram attributes to display in the legends the Color and Legend properties, as previously assigned in the Attributes tab;
  • and, when a scaled size is being used for the diagrams, push the Legend Entries for Diagram Size… button to configure the diagram symbol aspect in the legends. This opens the Data-defined Size Legend dialog whose options are described in Data-defined size legend.

When set, the diagram legend items (attributes with color and diagram size) are also displayed in the print layout legend, next to the layer symbology.

Fallstudien

Wir werden ein Beispiel zeigen und dem Alaskagrenzlayer ein Textdiagramm das Temperaturdaten von einem climate Vektorlayer zeigt überlagern. Beide Vektorlayer sind Teil des QGIS Beispieldatensatzes (siehe Abschnitt Beispieldaten herunterladen).

  1. Klicken Sie erst auf das addOgrLayer Vektorlayer hinzufügen Icon, browsen Sie zum QGIS Beispieldatensatzordner und laden Sie die beiden Vektorlayer alaska.shp und climate.shp.
  2. Doppelklicken Sie auf den climate Layer in der Kartenlegende um den Dialog Layereigenschaften zu öffnen.
  3. Click on the Diagrams tab and from the Diagram type selectString combo box, select ‚Text diagram‘.
  4. Im Darstellung Reiter wählen wir ein Hellblau als Hintergrundfarbe und im Reiter Größe stellen wir eine feste Größe von 18 mm ein.
  5. Im Reiter Position könnte die Platzierung auf ‚Um Punkt‘ eingestellt werden.
  6. Im Diagramm wollen wir die Werte der drei Spalten T_F_JAN, T_F_JUL und T_F_MEAN darstellen. Wählen Sie erst T_F_JAN als Attribute´ und klicken Sie den |signPlus| Knopf, dann ``T_F_JUL` und schließlich T_F_MEAN.
  7. Now click Apply to display the diagram in the QGIS main window.
  8. Sie können die Diagrammgröße im Größe Reiter anpassen. Aktivieren Sie radioButtonOn Skalierte Größe und stellen Sie die Größe des Diagramms auf Basis eines Attributes mit dem Maximalwert und dem Größe Menü ein. Wenn die Diagramme auf dem Bildschirm zu klein erscheinen können Sie das checkbox Kleine Diagramme vergrößern Kontrollkästchen aktivieren und die Minimalgröße des Diagramms definieren.
  9. Change the attribute colors by double clicking on the color values in the Assigned attributes field. Figure_diagrams_mapped gives an idea of the result.
  10. Finally, click OK.
../../../_images/climate_diagram.png

Diagramm aus Temperaturdaten auf einer Karte dargestellt

Behalten Sie im Hinterkopf dass im Reiter Position eine Datendefinierte Position der Diagramme möglich ist. Sie können hier Attribute verwenden um die Position des Diagramms zu definieren. Sie können auch eine maßstabsabhängige Sichtbarkeit im Darstellung Reiter einstellen.

The size and the attributes can also be an expression. Use the expression button to add an expression. See Ausdrücke chapter for more information and example.

Using data-defined override

As mentioned above, you can use some custom data-defined to tune the diagrams rendering:

  • position in Placement tab by filling X and Y fields
  • visibility in Appearance tab by filling the Visibility field

See Datendefinierte Übersteuerung für das Beschriften for more information.

Source Fields Properties

sourceFields The Source Fields tab provides information on fields related to the layer and helps you organize them.

The layer can be made editable using the toggleEditing Toggle editing mode. At this moment, you can modify its structure using the newAttribute New field and deleteAttribute Delete field buttons.

You can also rename fields by double-clicking its name. This is only supported for data providers like PostgreSQL, Oracle, Memory layer and some OGR layer depending on the OGR data format and version.

If set in the underlying data source or in the forms properties, the field’s alias is also displayed. An alias is a human readable field name you can use in the feature form or the attribute table. Aliases are saved in the project file.

Depending on the data provider, you can associate a comment with a field, for example at its creation. This information is retrieved and shown in the Comment column and is later displayed when hovering over the field label in a feature form.

Other than the fields contained in the dataset, virtual fields and Auxiliary Storage included, the Source Fields tab also lists fields from any joined layers. Depending on the origin of the field, a different background color is applied to it.

For each listed field, the dialog also lists read-only characteristics such as its type, type name, length and precision. When serving the layer as WMS or WFS, you can also check here which fields could be retrieved.

../../../_images/fields_properties.png

Source Field properties tab

Attributes Form Properties

formView The Attributes Form tab helps you set up the form to display when creating new features or querying existing one. You can define:

  • the look and the behavior of each field in the feature form or the attribute table (label, widget, constraints…);
  • the form’s structure (custom or autogenerated):
  • extra logic in Python to handle interaction with the form or field widgets.

At the top right of the dialog, you can set whether the form is opened by default when creating new features. This can be configured per layer or globally with the Suppress attribute form pop-up after feature creation option in the Settings ‣ Options ‣ Digitizing menu.

Customizing a form for your data

By default, when you click on a feature with the identify Identify Features tool or switch the attribute table to the form view mode, QGIS displays a basic form with predefined widgets (generally spinboxes and textboxes — each field is represented on a dedicated row by its label next to the widget). If relations are set on the layer, fields from the referencing layers are shown in an embedded frame at the bottom of the form, following the same basic structure.

This rendering is the result of the default Autogenerate value of the Attribute editor layout setting in the Layer properties ‣ Attributes Form tab. This property holds three different values:

  • Autogenerate: keeps the basic structure of „one row - one field“ for the form but allows to customize each corresponding widget.
  • Drag-and-drop designer: other than widget customization, the form structure can be made more complex eg, with widgets embedded in groups and tabs.
  • Provide ui file: allows to use a Qt designer file, hence a potentially more complex and fully featured template, as feature form.

The autogenerated form

When the Autogenerate option is on, the Available widgets panel shows lists of fields (from the layer and its relations) that would be shown in the form. Select a field and you can configure its appearance and behavior in the right panel:

The drag and drop designer

Choose Drag and drop designer from the Attribute editor layout combobox and you enable a Form Layout panel next to the Available widgets one. From this panel you can create an editor form with several tabs and named groups to present the attribute fields, as shown for example in figure_fields_form.

../../../_images/resulting_feature_form.png

Das Ergebnis eines integrierten Formulars mit Reitern und benannten Gruppen

To create the form, you can drag and drop fields from the Available Widgets panel to the Form Layout one to have fields added to your custom form and drag and drop fields inside the Form Layout to reorder their position.

You can also use categories (tab or group frames) to better structure the form. The first step is to use the signPlus icon to create a tab in which fields and groups will be displayed (see figure_fields_layout). You can create as many categories as you want. Use signMinus button to remove any unwanted elements. The next step will be to assign to each category the relevant fields, by simple drag and drop. You can use the same fields many times.

../../../_images/attribute_editor_layout.png

Dialog Attributeditorzusammenstellung um Kategorien zu erstellen

You can configure tabs or groups with a double-click. QGIS opens a form in which you can:

  • choose to hide or show the item label;
  • rename the category;
  • set over how many columns the fields under the category should be distributed;
  • enter an expression to control the category visibility. The expression will be re-evaluated everytime values in the form change and the tab or groupbox shown/hidden accordingly;
  • show the category as a group box (only available for tabs).

With a double-click on a field label, you can also specify whether the label of its widget should be visible or not in the form.

In case the layer is involved in one or many to many relations (see Creating one or many to many relations), referencing layers are listed in the Relations frame and their form can be embedded in the current layer form by drag-and-drop. Like the other items, double-click the relation label to configure some options:

  • choose to hide or show the item label;
  • show the link button;
  • show the unlink button.

Using custom ui-file

The Provide ui-file option allows you to use complex dialogs made with Qt-Designer. Using a UI-file allows a great deal of freedom in creating a dialog. Note that, in order to link the graphical objects (textbox, combobox…) to the layer’s fields, you need to give them the same name.

Use the Edit UI to define the path to the file to use.

You’ll find some example in the Creating a new form lesson of the QGIS Training Manual. For more advanced information, see https://nathanw.net/2011/09/05/qgis-tips-custom-feature-forms-with-python-logic/.

Enhance your form with custom functions

QGIS forms can have a Python function that is called when the dialog is opened. Use this function to add extra logic to your dialogs. The form code can be specified in three different ways:

  • load from the environment: use a function, for example in startup.py or from an installed plugin
  • load from an external file: a file chooser will appear in that case to allow you to select a Python file from your filesystem
  • provide code in this dialog: a Python editor will appear where you can directly type the function to use.

In all cases you must enter the name of the function that will be called (open in the example below).

Ein Beispiel ist (im Modul MyForms.py):

def open(dialog,layer,feature):
    geom = feature.geometry()
    control = dialog.findChild(QWidged,"My line edit")

Reference in Python Init Function like so: open

Configure the field behavior

The main part of the Attributes Form tab helps you set the type of widget used to fill or display values of the field, in the attribute table or the feature form: you can define how user interacts with each field and the values or range of values that are allowed to be added to each.

../../../_images/edit_widgets_dialog.png

Dialog um ein Bearbeitungselement für eine Attributspalte auszuwählen

Common settings

Regardless the type of widget applied to the field, there are some common properties you can set to control whether and how a field can be edited.

General options
  • Alias: a human readable name to use for fields. The alias will be displayed in the feature form, the attribute table, or in the Identify results panel. It can also be used as field name replacement in the expression builder, easing expressions understanding and reviews. Aliases are saved in project file.
  • Comment: displays the field’s comment as shown in the Source Fields tab, in a read-only state. This information is shown as tooltip when hovering over the field label in a feature form.
  • checkbox Editable: uncheck this option to set the field read-only (not manually modifiable) even when the layer is in edit mode. Note that checking this setting doesn’t override any edit limitation from the provider.
  • checkbox Label on top: places the field name above or beside the widget in the feature form.
Default values
  • Default value: for new features, automatically populates by default the field with a predefined value or an expression-based one. For example, you can:

    • use $x, $length, $area to automatically populate a field with the feature’s X coordinate, length, area or any geometric information at its creation;
    • increment a field by 1 for each new feature using maximum("field")+1;
    • save the feature creation datetime using now();
    • use variables in expressions, making it easier to e.g. insert the operator name (@user_full_name), the project file path (@project_path), …

    A preview of the resulting default value is displayed at the bottom of the widget.

    Bemerkung

    The Default value option is not aware of the values in any other field of the feature being created so it won’t be possible to use an expression combining any of those values i.e using an expression like concat(field1, field2) may not work.

  • checkbox Apply default value on update: whenever the feature attribute or geometry is changed, the default value is recalculated. This could be handy to save values like last user that modifies data, last time it was changed…

Constraints

You can constrain the value to insert in the field. This constraint can be:

  • checkbox Not null: requires the user to provide a value;
  • checkbox Unique: guarantee the inserted value to be unique throughout the field;
  • based on a custom expression: e.g. regexp_match(col0,'A-Za-z') to ensure that the value of the field col0 has only alphabetical letter. A short description can be added to help you remember the constraint.

Whenever a value is added or edited in a field, it’s submitted to the existing constraints and:

  • if it meets all the requirements, a green check is shown beside the field in the form;
  • if it does not meet all the requirements, then a yellow or red cross is displayed near the field. You can hover over the cross to remind which constraints are applied to the field and fix the value:
    • A yellow cross appears when the unmet constraint is an unenforced one and it does not prevent you to save the changes with the „wrong“ values;
    • A red cross can not be ignored and does not allow you to save your modifications until they meet the constraints. It appears when the checkbox Enforce constraint option is checked.

Edit widgets

Based on the field type, QGIS automatically determines and assigns a default widget type to it. You can then replace the widget with any other compatible with the field type. The available widgets are:

  • Checkbox: Displays a checkbox whose state defines the value to insert.
  • Classification: Only available when a categorized symbology is applied to the layer, displays a combo box with the values of the classes.
  • Color: Displays a color widget allowing to select a color; the color value is stored as a html notation in the attribute table.
  • Datum/Zeit: Stellt ein Linienfeld dar, das ein Kalender-Widget zum Öffnen eines Datums, einer Zeit oder beidem, darstellt. Der Spaltentyp muss Text sein. Sie könnne ein benutzerdefiniertes Format auswählen, einen Pop-up-Kalender, etc.
  • Enumeration: Opens a combo box with predefined values fetched from the database. This is currently only supported by the PostgreSQL provider, for fields of enum type.
  • Attachment: Uses a „Open file“ dialog to store file path in a relative or absolute mode. It can also be used to display a hyperlink (to document path), a picture or a web page.
  • Versteckt: Ein verstecktes Attribut ist unsichtbar. Der Anwender kann den Inhalt nicht sehen.
  • Key/Value: Displays a two-columns table to store sets of key/value pairs within a single field. This is currently supported by the PostgreSQL provider, for fields of hstore type.
  • List: Displays a single column table to add different values within a single field. This is currently supported by the PostgreSQL provider, for fields of array type.
  • Bereich: Erlaubt Ihnen numerische Werte eines bestimmten Wertebereichs festzulegen. Das Bearbeitungselement kann entweder ein Schieber oder ein Drehfeld sein.
  • Relation Reference: This widget lets you embed the feature form of the referenced layer on the feature form of the actual layer. See Creating one or many to many relations.
  • Text Edit (default): This opens a text edit field that allows simple text or multiple lines to be used. If you choose multiple lines you can also choose html content.
  • Unique Values: You can select one of the values already used in the attribute table. If ‚Editable‘ is activated, a line edit is shown with autocompletion support, otherwise a combo box is used.
  • Uuid Generator: Generates a read-only UUID (Universally Unique Identifiers) field, if empty.
  • Value Map: A combo box with predefined items. The value is stored in the attribute, the description is shown in the combo box. You can define values manually or load them from a layer or a CSV file.
  • Value Relation: Offers values from a related table in a combobox. You can select layer, key column and value column. Several options are available to change the standard behaviors: allow null value, order by value, allow multiple selections and use of auto-completer. The forms will display either a drop-down list or a line edit field when completer checkbox is enabled.

Tipp

Relative Path in Attachment widget

If the path which is selected with the file browser is located in the same directory as the .qgs project file or below, paths are converted to relative paths. This increases portability of a .qgs project with multimedia information attached.

Joins Properties

join The Joins tab allows you to join a loaded attribute table to a loaded vector layer. After clicking signPlus, the Add vector join dialog appears. As key columns, you have to define a join layer you want to connect with the target vector layer. Then, you have to specify the join field that is common to both the join layer and the target layer. Now you can also specify a subset of fields from the joined layer based on the checkbox checkbox Choose which fields are joined. As a result of the join, all information from the join layer and the target layer are displayed in the attribute table of the target layer as joined information. If you specified a subset of fields only these fields are displayed in the attribute table of the target layer.

If the target layer is editable, then some icons will be displayed in the attribute table next to fields, in order to inform their status:

  • joinNotEditable: the join layer is not configured to be editable. If you want to be able to edit join features from the target attribute table, then you have to check the option checkbox Editable join layer.
  • joinedLayerNotEditable: the join layer is well configured to be editable, but its current status is read only.
  • joinHasNotUpsertOnEdit: the join layer is editable but synchronization mechanisms are not activated. If you want to automatically add a feature in the join layer when a feature is created in the target layer, then you have to check the option checkbox Upsert on edit. Symmetrically, the option checkbox Delete cascade may be activated if you want to automatically delete join features.

Moreover, the checkbox Dynamic form option helps to synchronize join fields on the fly, according to the Target field. This way, constraints for join fields are also correctly updated. Note that it’s deactivated by default because it may be very time consuming if you have a lot of features or a myriad of joins.

Otherwise, the checkbox Cache join layer in virtual memory option allows to cache values in memory (without geometries) from the joined layer in order to speed up lookups.

QGIS currently has support for joining non-spatial table formats supported by OGR (e.g., CSV, DBF and Excel), delimited text and the PostgreSQL provider (see figure_joins).

../../../_images/join_attributes.png

Verknüpfe eine Attributtabelle zu einem vorhandenen Vektorlayer

Zusätzlich können Sie mit dem Vektorverknüpfung hinzufügen Dialog:

  • checkbox Index auf Feld erzeugen
  • checkbox Verknüpfte Felder wählen
  • Erstellen Sie einen checkbox :guilabel:`Benutzerdefinierten Feldnamen Präfix `

Auxiliary Storage Properties

The regular way to customize styling and labeling is to use data-defined properties as described in Datendefinierte Übersteuerung Setup. However, it may not be possible if the underlying data is read only. Moreover, configuring these data-defined properties may be very time consuming or not desirable! For example, if you want to fully use map tools coming with The Label Toolbar, then you need to add and configure more than 20 fields in your original data source (X and Y positions, rotation angle, font style, color and so on).

The Auxiliary Storage mechanism provides the solution to these limitations and awkward configurations. Auxiliary fields are a roundabout way to automatically manage and store these data-defined properties (labels, diagram, symbology…) in a SQLite database thanks to editable joins. This allows you to store properties for layers that aren’t editable.

A tab is available in vector layer properties dialog to manage auxiliary storage:

../../../_images/auxiliary_storage_tab.png

Auxiliary Storage tab

Labeling

Considering that the data source may be customized thanks to data-defined properties without being editable, labeling map tools described in The Label Toolbar are always available as soon as labeling is activated.

Actually, the auxiliary storage system needs an auxiliary layer to store these properties in a SQLite database (see Auxiliary storage database). Its creation process is run the first time you click on the map while a labeling map tool is currently activated. Then, a window is displayed, allowing you to select the primary key to use for joining (to ensure that features are uniquely identified):

../../../_images/auxiliary_storage_key.png

Auxiliary Layer creation dialog

As soon as an auxiliary layer is configured for the current data source, you can retrieve its information in the tab:

../../../_images/auxiliary_storage_tabkey.png

Auxiliary Layer key

The auxiliary layer now has these characteristics:

  • the primary key is ID,
  • there are 0 features using an auxiliary field,
  • there are 0 auxiliary fields.

Now that the auxiliary layer is created, you can edit the layer labels. Click on a label while the changeLabelProperties Change Label map tool is activated, then you can update styling properties like sizes, colors, and so on. The corresponding data-defined properties are created and can be retrieved:

../../../_images/auxiliary_storage_fields.png

Auxiliary Fields

As you can see in the figure above, 21 fields are automatically created and configured for labeling. For example, the FontStyle auxiliary field type is a String and is named labeling_fontstyle in the underlying SQLite database. There is also 1 feature which is currently using these auxiliary fields.

Notice that the icon dataDefineOn is displayed in the Labels properties tab indicating that the data-defined override options are set correctly:

../../../_images/auxiliary_storage_dd.png

Data-defined properties automatically created

Otherwise, there’s another way to create an auxiliary field for a specific property thanks to the dataDefined data-defined override button. By clicking on Store data in the project, an auxiliary field is automatically created for the Opacity field. If you click on this button whereas the auxiliary layer is not created yet, then the window Auxiliary Layer creation dialog is first displayed to select the primary key to use for joining.

Symbolisierung

Like the method described above for customizing labels, auxiliary fields can also be used to stylize symbols and diagrams. To do this, click on dataDefined Data-defined override and select Store data in the project for a specific property. For example, the Fill color field:

../../../_images/auxiliary_storage_symbol.png

Data-defined property menu for symbol

There are different attributes for each symbol (e.g. fill style, fill color, stroke color, etc…), so each auxiliary field representing an attribute requires a unique name to avoid conflicts. After selecting Store data in the project, a window opens and displays the Type of the field and prompts you to enter a unique name for the auxiliary field. For example, when creating a Fill color auxiliary field the following window opens:

../../../_images/auxiliary_storage_symbol_name.png

Name of the auxiliary field for a symbol

Once created, the auxiliary field can be retrieved in the auxiliary storage tab:

../../../_images/auxiliary_storage_symbol_field.png

Auxiliary field symbol

Attribute table and widgets

Auxiliary fields can be edited using the attribute table. However, not all auxiliary fields are initially visible in the attribute table.

Auxiliary fields representing attributes of a layer’s symbology, labeling, appearance, or diagrams will appear automatically in the attribute table. The exception are attributes that can be modified using the Label Toolbar which are hidden by default. Auxiliary fields representing a Color have a widget Color set by default, otherwise auxiliary fields default to the Text Edit widget.

Auxiliary fields that represent attributes that can be modified using the Label toolbar are Hidden in the attribute table by default. To make a field visible, open the Attribute Form properties tab and change the value of an auxiliary field Widget Type from Hidden to another relevant value. For example, change the auxiliary_storage_labeling_size to Text Edit or change auxiliary_storage_labeling_color to the Color widget. Those fields will now be visible in the attribute table.

Auxiliary fields in the attribute table will appear like the following image:

../../../_images/auxiliary_storage_widgets.png

Form with auxiliary fields

Management

The Auxiliary Layer menu allows you to manage the auxiliary fields:

../../../_images/auxiliary_storage_actions.png

Auxiliary layer management

The first item Create is disabled in this case because the auxiliary layer is already created. But in case of a fresh work, you can use this action to create an auxiliary layer. As explained in Labeling, a primary key will be needed then.

The Clear action allows to keep all auxiliary fields, but remove their contents. This way, the number of features using these fields will fall to 0.

The Delete action completely removes the auxiliary layer. In other words, the corresponding table is deleted from the underlying SQLite database and properties customization are lost.

Finally, the Export action allows to save the auxiliary layer as a new vector layer. Note that geometries are not stored in auxiliary storage. However, in this case, geometries are exported from the original data source too.

Auxiliary storage database

When you save your project with the .qgs format, the SQLite database used for auxiliary storage is saved at the same place but with the extension .qgd.

For convenience, an archive may be used instead thanks to the .qgz format. In this case, .qgd and .qgs files are both embedded in the archive.

Actions Properties

action QGIS bietet die Möglichkeit, Aktionen auf Basis von Attributen einer Ebene durchzuführen. Dies kann für eine Vielzahl von Aktionen genutzt werden, z.B. um ein Programm mit Abfragen aus der Attributdatenbank zu füttern oder um Parameter an ein Web-Reporting-Tool weiterzugeben.

../../../_images/action_dialog.png

Überblick über den Dialog Aktionen mit einigen Beispielaktionen

Aktionen auf Basis von Attributen sind sinnvoll wenn sie häufig eine externe Anwendung starten oder eine Internetseite auf Basis von einem oder mehreren Werten in Ihrem Vektorlayer visualisieren wollen. Sie sind in 6 Typen aufgeteilt und können wie folgt verwendet werden:

  • Allgemein, Mac, Windows und Unix Aktionen starten einen externen Prozess.
  • Python Aktionen führen einen Python-Ausdruck aus.
  • Allgemeine und Pythonaktionen sind überall sichtbar.
  • Mac, Windows und Unix Aktionen sind nur sichtbar auf der entsprechenden Plattform (z.B. können Sie drei ‚Bearbeiten‘ Aktionen definieren um einen Editor zu öffnen und die Benutzer können nur die eine ‚Bearbeiten‘ Aktion für Ihr Betriebssystem sehen und ausführen um den Editor zu starten).

There are several examples included in the dialog. You can load them by clicking on Create Default Actions. To edit any of the examples, double-click its row. One example is performing a search based on an attribute value. This concept is used in the following discussion.

The checkbox Show in Attribute Table allows you to display in the attribute table dialog the checked feature-scoped actions, either as Combo Box or as Separate Buttons (see Configuring the columns).

Aktionen definieren

To define an attribute action, open the vector Layer Properties dialog and click on the Actions tab. In the Actions tab, click the signPlus Add a new action to open the Edit Action dialog.

Select the action Type and provide a descriptive name for the action. The action itself must contain the name of the application that will be executed when the action is invoked. You can add one or more attribute field values as arguments to the application. When the action is invoked, any set of characters that start with a % followed by the name of a field will be replaced by the value of that field. The special characters %% will be replaced by the value of the field that was selected from the identify results or attribute table (see using_actions below). Double quote marks can be used to group text into a single argument to the program, script or command. Double quotes will be ignored if preceded by a backslash.

The Action Scopes allows you to define where the action should be available. You have 4 different choices:

  1. Feature Scope: action is available when right click in the cell within the attribute table.
  2. Field Scope: action is available when right click in the cell within the attribute table, in the feature form and in the default action button of the main toolbar.
  3. Layer Scope: action is available in the action button in the attribute table toolbar. Be aware that this type of action involves the entire layer and not the single features.
  4. Canvas: action is available in the main action button in the toolbar.

Wenn Sie Feldnamen vorfinden die Substrings anderer Feldnamen sind (z.B., col1 und col10) sollten Sie das angeben indem Sie den Feldnamen (und den % Buchstaben) mit eckigen Klammern umrunden (z.B. [%col10]). Hiermit wird vermieden dass der %col10 Feldname mit de, %col1 Feldnamen mit einem 0 am Ende verwechselt wird. Die Klammern werden von QGS entfernt wenn es im Wert des Feldes ersetzt. Wenn Sie wollen dass das zu ersetzende Feld von eckigen Klammern umrandet wird verwenden Sie ein zweites Set wie hier:[[%col10]].

Wenn Sie das Objekte abfragen Werkzeug verwenden, können Sie den Identifikationsergebnis Dialog öffnen. Es enthält eine (Abgeleitet) Item das layertyprelevante Informationen enthält. Die Werte in diesem Element können auf ähnliche Weise den anderen Feldern zugeordnet werden indem dem Abgeleitet Feldnamen ein (Derived) vorangeht. Zum Beispiel hat ein Punktlayer ein X und Y Feld und die Werte dieser Felder können in der Aktion mit %(Derived).X und %(Derived).Y verwendet werden. Die Abgeleitet Attribute sind nur in der Objekte abfragen Dialog Box erhältlich, jedoch nicht in der Attributtabelle Dialogbox.

Two example actions are shown below:

  • konqueror https://www.google.com/search?q=%nam
  • konqueror https://www.google.com/search?q=%%

In the first example, the web browser konqueror is invoked and passed a URL to open. The URL performs a Google search on the value of the nam field from our vector layer. Note that the application or script called by the action must be in the path, or you must provide the full path. To be certain, we could rewrite the first example as: /opt/kde3/bin/konqueror https://www.google.com/search?q=%nam. This will ensure that the konqueror application will be executed when the action is invoked.

Das zweite Beispiel nutzt den Ausdruck %%, welcher unabhängig ist von einem speziellen Feld. Beim Ausführen des Befehls wird der Ausdruck %% durch den Wert des jeweils selektierten Feldes aus Objekte abfragen oder der Attributtabelle ersetzt.

Aktionen anwenden

QGIS offers many ways to execute actions you enabled on a layer. Depending on their settings, they can be available:

  • in the drop-down menu of actionRun Run Feature Action button from the Attributes toolbar or Attribute table dialog;
  • when right-clicking a feature with the identify Identify Features tool (see Identifying Features for more information);
  • from the Identify Results panel, under the Actions section;
  • as items of an Actions column in the Attribute Table dialog.

Wenn Sie eine Aktion mit %% Notation verwenden, machen Sie einen Rechtsklick auf den Feldwert im Objekte abfragen Dialog oder im Attributtabelle Dialog den Sie der Anwendung oder dem Skript übergeben wollen.

In einem weiteren Beispiel soll gezeigt werden, wie Attributwerte eines Vektorlayers abgefragt und in eine Textdatei mit Hilfe der Bash und des echo Kommandos geschrieben werden (funktioniert also nur unter nix und evtl. osx ). Der Abfragelayer enthält die Felder Art taxon_name, Latitude lat und Longitude long. Wir möchten jetzt eine räumliche Selektion von Örtlichkeiten machen und diese Feldwerte in eine Textdatei für den ausgewählten Datensatz (in der QGIS Kartenansicht in gelb gezeigt) exportieren. Hier ist die Aktion, um dies zu erreichen:

bash -c "echo \"%taxon_name %lat %long\" >> /tmp/species_localities.txt"

Nachdem ein paar Orte auf dem Bildschirm ausgewählt wurden (diese erscheinen gelb hinterlegt), starten wir die Aktion mit der rechten Maustaste über den Dialog Abfrageergebnisse und können danach in der Textdatei die Ergebnisse ansehen:

Acacia mearnsii -34.0800000000 150.0800000000
Acacia mearnsii -34.9000000000 150.1200000000
Acacia mearnsii -35.2200000000 149.9300000000
Acacia mearnsii -32.2700000000 150.4100000000

As an exercise, we can create an action that does a Google search on the lakes layer. First, we need to determine the URL required to perform a search on a keyword. This is easily done by just going to Google and doing a simple search, then grabbing the URL from the address bar in your browser. From this little effort, we see that the format is https://www.google.com//search?q=QGIS, where QGIS is the search term. Armed with this information, we can proceed:

  1. Laden Sie den Layer file:lakes.shp.

  2. Öffnen Sie den Layereigenschaften Dialog indem Sie einen Doppelklick auf den Layer in der Legende machen und wählen Sie Eigenschaften aus dem Popup-Menü.

  3. Click on the Actions tab.

  4. Click signPlus Add a new action.

  5. Choose the Open action type,

  6. Geben Sie einen Namen für die Aktion ein, z.B. Google Search.

  7. Additionally you can add a Short Name or even an Icon.

  8. Choose the action Scope. See Aktionen definieren for further information. Leave the default settings for this example.

  9. Für diese Aktion ist es notwendig den Namen des externen Programms anzugeben. In diesem Fall können wir Firefox verwenden. Wenn das Programm sich nicht im Pfad befindet müssen Sie den vollständigen Pfad angeben.

  10. Following the name of the external application, add the URL used for doing a Google search, up to but not including the search term: https://www.google.com//search?q=

  11. The text in the Action field should now look like this: https://www.google.com//search?q=

  12. Click on the drop-down box containing the field names for the lakes layer. It’s located just to the left of the Insert button.

  13. From the drop-down box, select ‚NAMES‘ and click Insert.

  14. Die Aktion sieht nun so aus:

    https://www.google.com//search?q=[%NAMES%]

  15. To finalize and add the action, click the OK button.

../../../_images/add_action_edit.png

Edit action dialog configured with the example

Damit ist die Aktion fertig für den Einsatz. Der gesamte Befehl der Aktion sollte folgendermaßen aussehen:

https://www.google.com//search?q=[%NAMES%]

Damit ist die Aktion fertig für den Einsatz. Schließen Sie den Eigenschaften Dialog und zoomen Sie in einen Bereich Ihrer Wahl. Stellen Sie sicher, dass der Layer lakes in der Legende aktiviert ist. Nun identifizieren Sie einen See. In der Ergebnisanzeige sollte nun die Aktion sichtbar sein:

../../../_images/action_identifyaction.png

Wählen Sie ein Objekt und eine Aktion aus

When we click on the action, it brings up Firefox and navigates to the URL https://www.google.com/search?q=Tustumena. It is also possible to add further attribute fields to the action. Therefore, you can add a + to the end of the action text, select another field and click on Insert Field. In this example, there is just no other field available that would make sense to search for.

Sie können auch mehrere Aktionen für einen Layer definieren. Sie alle werden dann bei der Abfrage von Objekten im Identifikationsergebnis Dialog angezeigt.

Sie können auch die aus der Attributtabelle aufrufen, indem Sie eine Zeile mit der rechten Maustaste auswählen und dann die Aktion aus dem Pop-up-Menü wählen.

Sie sehen, man kann sich eine Vielzahl interessanter Aktionen ausdenken. Wenn Sie z.B. einen Punktlayer mit einzelnen Punkten haben, an denen Photos geschossen wurden, dann können Sie eine Aktion erstellen, über die Sie dann das entsprechende Foto anzeigen lassen können, wenn Sie auf den Punkt in der Karte klicken. Man kann auch zu bestimmten Attributen webbasierte Information ablegen (z.B. in einer HTML-Datei) und diese dann über eine Aktion anzeigen lassen, etwa so wie in dem Google Beispiel.

Wir können auch komplexere Beispiele erstellen, indem wir z.B. Python Aktionen verwenden.

Usually, when we create an action to open a file with an external application, we can use absolute paths, or eventually relative paths. In the second case, the path is relative to the location of the external program executable file. But what about if we need to use relative paths, relative to the selected layer (a file-based one, like Shapefile or SpatiaLite)? The following code will do the trick:

command = "firefox"
imagerelpath = "images_test/test_image.jpg"
layer = qgis.utils.iface.activeLayer()
import os.path
layerpath = layer.source() if layer.providerType() == 'ogr'
  else (qgis.core.QgsDataSourceURI(layer.source()).database()
    if layer.providerType() == 'spatialite' else None)
path = os.path.dirname(str(layerpath))
image = os.path.join(path,imagerelpath)
import subprocess
subprocess.Popen( [command, image ] )

Wir müssen uns nur ins Gedächtnis rufen dass es sich um eine Python Aktion handelt und dass das Ändern der command und imagerelpath Variablen auf unsere Bedürfnisse angepasst wird.

Was aber wenn der relative Pfad relativ zur (gespeicherten) Projektdatei sein muss? Der Code der Python Aktion würde wie folgt lauten:

command = "firefox"
imagerelpath = "images/test_image.jpg"
projectpath = qgis.core.QgsProject.instance().fileName()
import os.path
path = os.path.dirname(str(projectpath)) if projectpath != '' else None
image = os.path.join(path, imagerelpath)
import subprocess
subprocess.Popen( [command, image ] )

Ein anderes Python Aktion Beispiel ist das mit wir dem Projekt neue Layer hinzufügen können. Z.B. wird in den folgenden Beispielen dem Projekt ein Vektorlayer beziehungsweise ein Rasterlayer hinzugefügt. Die Namen der Dateien, die dem Projekt hinzugefügt werden sollen, und die Namen, die den Layern gegeben werden, sind datengesteuert (filename und layername sind Spaltennamen der Attributtabelle des Vektorlayers in dem die Aktion erstellt wurde):

qgis.utils.iface.addVectorLayer('/yourpath/[% "filename" %].shp',
  '[% "layername" %]', 'ogr')

Um eine Rasterdatei hinzuzufügen (ein TIF-Bild in diesem Beispiel) wird daraus:

qgis.utils.iface.addRasterLayer('/yourpath/[% "filename" %].tif',
  '[% "layername" %]')

Display Properties

display The Display tab helps you configure fields to use for feature identification:

  • The Display name: based on a field or an expression. This is:
    • the label shown on top of the feature information in the Identify tool results;
    • the field used in the locator bar when looking for features in all layers;
    • the feature identifier in the attribute table form view;
    • the map tip information, i.e. the message displayed in the map canvas when hovering over a feature of the active layer with the mapTips Show Map Tips icon pressed. Applicable when no HTML Map Tip is set.
  • The HTML Map Tip is specifically created for the map tips: it’s a more complex and full HTML text mixing fields, expressions and html tags (multiline, fonts, images, hyperlink…).
../../../_images/display_html.png

HTML-Code für Kartenhinweis

To activate map tips, select the menu option View ‣ Show Map Tips or click on the mapTips Show Map Tips icon of the Attributes Toolbar. Map tip is a cross-session feature meaning that once activated, it stays on and apply to any layer in any project, even in future QGIS sessions until it’s toggled off.

../../../_images/map_tip.png

Kartenhinweis erstellt mit HTML-Code

Rendering Properties

Maßstabsabhängige Sichtbarkeit

You can set the Maximum (inclusive) and Minimum (exclusive) scale, defining a range of scale in which features will be visible. Out of this range, they are hidden. The mapIdentification Set to current canvas scale button helps you use the current map canvas scale as boundary of the range visibility. See Maßstabsabhängige Layeranzeige for more information.

Simplify geometry

QGIS offers support for on-the-fly feature generalisation. This can improve rendering times when drawing many complex features at small scales. This feature can be enabled or disabled in the layer settings using the checkbox Simplify geometry option. There is also a global setting that enables generalisation by default for newly added layers (see global simplification for more information).

../../../_images/simplify_rendering.png

Dialog Layergeometrien vereinfachen

Bemerkung

Objektgeneralisierung, kann in einigen Fällen, Artefakte in Ihre gerenderte Ausgabe einführen. Dies können Splitter zwischen Polygonen und ungenau Darstellung bei der Verwendung von Offset-basierten Symbolayern sein.

While rendering extremely detailed layers (e.g. polygon layers with a huge number of nodes), this can cause layout exports in PDF/SVG format to be huge as all nodes are included in the exported file. This can also make the resultant file very slow to work with/open in other programs.

Aktivieren von checkbox Force layer to render as raster zwingt diese Layer dazu gerastert zu werden, so dass die exportierten Dateien nicht alle enthaltenen Knoten in diesen Layern enthalten müssen und die Wiedergabe daher beschleunigt wird.

You can also do this by forcing the layout to export as a raster, but that is an all-or-nothing solution, given that the rasterisation is applied to all layers.

Refresh layer at interval (seconds): set a timer to automatically refresh individual layers at a matching interval. Canvas updates are deferred in order to avoid refreshing multiple times if more than one layer has an auto update interval set.

Depending on the data provider (e.g. PostgreSQL), notifications can be sent to QGIS when changes are applied to the data source, out of QGIS. Use the checkbox Refresh layer on notification option to trigger an update. You can also limit the layer refresh to a specific message set in the checkbox Only if message is text box.

Variables Properties

expression The Variables tab lists all the variables available at the layer’s level (which includes all global and project’s variables).

It also allows the user to manage layer-level variables. Click the signPlus button to add a new custom layer-level variable. Likewise, select a custom layer-level variable from the list and click the signMinus button to remove it.

More information on variables usage in the General Tools Storing values in Variables section.

Metadata Properties

editMetadata The Metadata tab provides you with options to create and edit a metadata report on your layer. Information to fill concern:

  • the data Identification: basic attribution of the dataset (parent, identifier, title, abstract, language…);
  • the Categories the data belongs to. Alongside the ISO categories, you can add custom ones;
  • the Keywords to retrieve the data and associated concepts following a standard based vocabulary;
  • the Access to the dataset (licenses, rights, fees, and constraints);
  • the Extent of the dataset, either spatial one (CRS, map extent, altitudes) or temporal;
  • the Contact of the owner(s) of the dataset;
  • the Links to ancillary resources and related information;
  • the History of the dataset.

A summary of the filled information is provided in the Validation tab and helps you identify potential issues related to the form. You can then either fix them or ignore them.

Metadata are currently saved in the project file. It can also be saved as an .XML file alongside file based layers or in a local .sqlite database for remote layers (e.g. PostGIS).

Dependencies Properties

dependencies The Dependencies tab allows to declare data dependencies between layers. A data dependency occurs when a data modification in a layer, not by direct user manipulation, may modify data of other layers. This is the case for instance when geometry of a layer is updated by a database trigger or custom PyQGIS scripting after modification of another layer’s geometry.

In the Dependencies tab, you can select any layers which may externally alter the data in the current layer. Correctly specifying dependent layers allows QGIS to invalidate caches for this layer when the dependent layers are altered.

Legend Properties

legend The Legend properties tab provides you with advanced settings for the Layers panel and/or the print layout legend. These options include:

  • checkbox Text on symbols: In some cases it can be useful to add extra information to the symbols in the legend. With this frame, you can affect to any of the symbols used in the layer symbology a text that is displayed over the symbol, in both Layers panel and print layout legend. This mapping is done by typing each text next to the symbol in the table widget or filling the table using the Set Labels from Expression button. Text appearance is handled through the font and color selector widgets of the Text Format button.
../../../_images/text_legend_symbols.png

Setting text on symbols (left) and its rendering in the Layers panel (right)

  • a list of widgets you can embed within the layer tree in the Layers panel. The idea is to have a way to quickly access some actions that are often used with the layer (setup transparency, filtering, selection, style or other stuff…).

    By default, QGIS provides transparency widget but this can be extended by plugins registering their own widgets and assign custom actions to layers they manage.

QGIS Server Properties

overlay The QGIS Server tab consists of Description, Attribution, MetadataURL, and LegendUrl sections.

You can add or edit a title and abstract for the layer in the Description section. It’s also possible to define a Keyword list here. These keyword lists can be used in a metadata catalog. If you want to use a title from an XML metadata file, you have to fill in a link in the DataUrl field.

Use Attribution to get attribute data from an XML metadata catalog.

In MetadataUrl, you can define the general path to the XML metadata catalog. This information will be saved in the QGIS project file for subsequent sessions and will be used for QGIS server.

Im Abschnitt LegendenUrl, können Sie der URL eines Legendenbilds in dem URL Feld anbieten. Sie können das Format Drop-Down-Menü nutzen, um das entsprechende Format des Bilds anzuwenden. Zur Zeit werden png, jpg und jpeg Formate unterstützt.

../../../_images/vector_server_properties.png

QGIS Server tab in vector layers properties dialog

Digitizing Properties

digitizing The Digitizing tab gives access to options that help to ensure the quality of digitized geometries.

../../../_images/vector_digitizing_properties.png

The QGIS Digitizing tab in the vector layers properties dialog

Automatic Fixes

Options in the Automatic Fixes section will directly affect the vertices of any geometry which is added or modified. If the checkbox Remove duplicate nodes option is checked, any two subsequent vertices with exactly the same coordinates will be removed. If the Geometry precision is set, all vertices will be rounded to the closest multiple of the configured geometry precision. The rounding will happen in the layer coordinate reference system. Z and M values are not rounded. With many map tools, a grid is shown on the canvas while digitizing.

Geometry Checks

In the Geometry checks section, additional validations on a per geometry basis can be activated. Immediately after any geometry modification, failures in these checks are reported to the user in the geometry validation panel. As long as a check is failing, it is not possible to save the layer. The checkbox Is valid check will run basic validity checks like self intersection on geometries.

Topology Checks

In the Topology checks section, additional topology validation checks can be activated. Topology checks will be executed when the user saves the layer. Check errors will be reported in the geometry validation panel. As long as validation errors are present, the layer can not be saved. Topology checks are executed in the area of the bounding box of the modified features. Since other features may be present in the same area, topological errors concerning these features are reported as well as errors introduced in the current edit session.

Topology check option Illustration
The checkbox Gap check will check for gaps between neighbouring polygons. ../../../_images/gapcheck.png
The checkbox Overlap check will check for overlaps between neighbouring polygons. ../../../_images/overlapcheck.png
The checkbox Missing vertex check will check for shared boundaries of neighbouring polygons where one border misses a vertex which is present on the other one. ../../../_images/missingvertexcheck.png