Algorithms Include

Python Code Sample

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

Output Types

Directory

  • Save to a Temporary Directory

  • Save to Directory

  • Skip Output

  • Save to a Temporary Directory

  • Save to Directory

File

  • Save to a Temporary File

  • Save to File…

  • Skip Output

  • Save to a Temporary File

  • Save to File…

Vrstva

  • Create Temporary Layer (TEMPORARY_OUTPUT)

  • Save to File…

  • Save to Geopackage…

  • Save to Database Table…

The file encoding can also be changed here.

  • Create Temporary Layer (TEMPORARY_OUTPUT)

  • Save to File…

  • Save to Geopackage…

  • Save to Database Table…

  • Append to Layer…

The file encoding can also be changed here.

  • Skip Output

  • Create Temporary Layer (TEMPORARY_OUTPUT)

  • Save to File…

  • Save to Geopackage…

  • Save to Database Table…

The file encoding can also be changed here.

Extent Dropdown

Available methods are:

  • Calculate from layer…: uses extent of a layer loaded in the current project

  • Calculate from layout map…: uses extent of a layout map item in the active project

  • Calculate from bookmark…: uses extent of a saved bookmark

  • Use map canvas extent

  • Draw on canvas: click and drag a rectangle delimiting the area to take into account

  • Enter the coordinates as xmin, xmax, ymin, ymax

Geometric predicates

Geometric predicates are boolean functions used to determine the spatial relation a feature has with another by comparing whether and how their geometries share a portion of space.

../../../_images/selectbylocation.png

Looking for spatial relations between layers

Using the figure above, we are looking for the green circles by spatially comparing them to the orange rectangle feature. Available geometric predicates are:

Intersect

Tests whether a geometry intersects another. Returns 1 (true) if the geometries spatially intersect (share any portion of space - overlap or touch) and 0 if they don’t. In the picture above, this will return circles 1, 2 and 3.

Contain

Returns 1 (true) if and only if no points of b lie in the exterior of a, and at least one point of the interior of b lies in the interior of a. In the picture, no circle is returned, but the rectangle would be if you would look for it the other way around, as it contains circle 1 completely. This is the opposite of are within.

Disjoint

Returns 1 (true) if the geometries do not share any portion of space (no overlap, not touching). Only circle 4 is returned.

Equal

Returns 1 (true) if and only if geometries are exactly the same. No circles will be returned.

Touch

Tests whether a geometry touches another. Returns 1 (true) if the geometries have at least one point in common, but their interiors do not intersect. Only circle 3 is returned.

Overlap

Tests whether a geometry overlaps another. Returns 1 (true) if the geometries share space, are of the same dimension, but are not completely contained by each other. Only circle 2 is returned.

Are within

Tests whether a geometry is within another. Returns 1 (true) if geometry a is completely inside geometry b. Only circle 1 is returned.

Cross

Returns 1 (true) if the supplied geometries have some, but not all, interior points in common and the actual crossing is of a lower dimension than the highest supplied geometry. For example, a line crossing a polygon will cross as a line (true). Two lines crossing will cross as a point (true). Two polygons cross as a polygon (false). In the picture, no circles will be returned.

Notes on algorithms

Varování

Geometry modification only

This operation modifies only the features geometry. The attribute values of the features are not modified, although properties such as area or length of the features will be modified by the overlay operation. If such properties are stored as attributes, those attributes will have to be manually updated.

Raster data types

Simplified list

  • 0 — Byte (Eight bit unsigned integer (quint8))

  • 1 — Int16 (Sixteen bit signed integer (qint16))

  • 2 — UInt16 (Sixteen bit unsigned integer (quint16))

  • 3 — UInt32 (Thirty two bit unsigned integer (quint32))

  • 4 — Int32 (Thirty two bit signed integer (qint32))

  • 5 — Float32 (Thirty two bit floating point (float))

  • 6 — Float64 (Sixty four bit floating point (double))

Available options depend on the GDAL version built with QGIS (see Help ► About menu)

Without user input (native)

  • 0 — Byte (Eight bit unsigned integer (quint8))

  • 1 — Int16 (Sixteen bit signed integer (qint16))

  • 2 — UInt16 (Sixteen bit unsigned integer (quint16))

  • 3 — Int32 (Thirty two bit signed integer (qint32))

  • 4 — UInt32 (Thirty two bit unsigned integer (quint32))

  • 5 — Float32 (Thirty two bit floating point (float))

  • 6 — Float64 (Sixty four bit floating point (double))

  • 7 — CInt16 (Complex Int16)

  • 8 — CInt32 (Complex Int32)

  • 9 — CFloat32 (Complex Float32)

  • 10 — CFloat64 (Complex Float64)

Available options depend on the GDAL version built with QGIS (see Help ► About menu)

Without user input

  • 0 — Byte (Eight bit unsigned integer (quint8))

  • 1 — Int16 (Sixteen bit signed integer (qint16))

  • 2 — UInt16 (Sixteen bit unsigned integer (quint16))

  • 3 — UInt32 (Thirty two bit unsigned integer (quint32))

  • 4 — Int32 (Thirty two bit signed integer (qint32))

  • 5 — Float32 (Thirty two bit floating point (float))

  • 6 — Float64 (Sixty four bit floating point (double))

  • 7 — CInt16 (Complex Int16)

  • 8 — CInt32 (Complex Int32)

  • 9 — CFloat32 (Complex Float32)

  • 10 — CFloat64 (Complex Float64)

Available options depend on the GDAL version built with QGIS (see Help ► About menu)

With user input

  • 0 — Use Input Layer Data Type

  • 1 — Byte (Eight bit unsigned integer (quint8))

  • 2 — Int16 (Sixteen bit signed integer (qint16))

  • 3 — UInt16 (Sixteen bit unsigned integer (quint16))

  • 4 — UInt32 (Thirty two bit unsigned integer (quint32))

  • 5 — Int32 (Thirty two bit signed integer (qint32))

  • 6 — Float32 (Thirty two bit floating point (float))

  • 7 — Float64 (Sixty four bit floating point (double))

  • 8 — CInt16 (Complex Int16)

  • 9 — CInt32 (Complex Int32)

  • 10 — CFloat32 (Complex Float32)

  • 11 — CFloat64 (Complex Float64)

Available options depend on the GDAL version built with QGIS (see Help ► About menu)