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Cartography

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Align points to features

Calculates the rotation required to align point features with their nearest feature from another reference layer. A new field is added to the output layer which is filled with the angle (in degrees, clockwise) to the nearest reference feature.

Optionally, the output layer's symbology can be set to automatically use the calculated rotation field to rotate marker symbols. If desired, a maximum distance to use when aligning points can be set, to avoid aligning isolated points to distant features.

Hint

This algorithm is designed for use cases like aligning building point symbols to follow the nearest road direction.

checkbox Allows :ref:`features in-place modification <processing_inplace_edit>` of point features

Parameters

Label Name Type Description
Input layer INPUT [vector: point] Point features to calculate the rotation for
Reference layer REFERENCE_LAYER [vector: geometry] Layer to find the closest feature from for rotation calculation

Maximum distance to consider

Optional

 MAX_DISTANCE

[numeric: double]

Default: Not set

 If no reference feature is found within this distance, no rotation is assigned to the point feature.
Angle field name FIELD_NAME

[string]

Default: 'rotation'

 Field in which to store the rotation value.
Automatically apply symbology APPLY_SYMBOLOGY

[boolean]

Default: True

 Rotates the symbol marker of the features using the angle field value
Aligned layer OUTPUT

[vector: point]

Default: [Save to temporary file]

 Specify the rotated output vector layer. :ref:`One of <output_parameter_widget>`:

Outputs

Label Name Type Description
Aligned layer OUTPUT [vector: point] The point layer appended with a rotation field. If loaded to QGIS, it is applied by default the input layer symbology, with a data-defined rotation of its marker symbol.

Python code

Algorithm ID: native:angletonearest

Combine style databases

Combines multiple QGIS style databases into a single style database. If items of the same type with the same name exist in different source databases these will be renamed to have unique names in the output combined database.

.. seealso:: :ref:`qgisstylefromproject`

Parameters

Label Name Type Description
Input databases INPUT [file] [list] Files containing QGIS style items
Objects to combine OBJECTS [enumeration] [list]

Types of style items in the input databases you would like to put in the new database. These can be:
Output style database OUTPUT

[file]

Default: [Save to temporary file]

 Output :file:`.XML` file combining the selected style items. :ref:`One of <output_parameter_widget>`:

Outputs

Label Name Type Description
Color ramp count COLORRAMPS [numeric: integer] Number of color ramps
Label settings count LABELSETTINGS [numeric: integer] Number of label settings
Output style database OUTPUT [file] Output :file:`.XML` file combining the selected style items
Symbol count SYMBOLS [numeric: integer] Number of symbols
Text format count TEXTFORMATS [numeric: integer] Number of text formats

Python code

Algorithm ID: native:combinestyles

Create categorized renderer from styles

Sets a vector layer's renderer to a categorized renderer using matching symbols from a style database. If no style file is specified, symbols from the user's current :ref:`symbol library <vector_symbol_library>` are used instead.

A specified expression or field is used to create categories for the renderer. Each category is individually matched to the symbols which exist within the specified QGIS XML style database. Whenever a matching symbol name is found, the category's symbol will be set to this matched symbol.

If desired, outputs can also be tables containing lists of the categories which could not be matched to symbols, and symbols which were not matched to categories.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Vector layer to apply a categorized style to
Categorize using expression FIELD [expression] Field or expression to categorize the features
Style database (leave blank to use saved symbols) STYLE [file] File (:file:`.XML`) containing the symbols to apply to the input layer categories. The file can be obtained from the Style Manager :ref:`Share symbols <share_symbols>` tool. If no file is specified, QGIS local symbols library is used.
Use case-sensitive match to symbol names CASE_SENSITIVE

[boolean]

Default: False

 If True (checked), applies a case sensitive comparison between the categories and symbols names
Ignore non-alphanumeric characters while matching TOLERANT

[boolean]

Default: False

 If True (checked), non-alphanumeric characters in the categories and symbols names will be ignored, allowing greater tolerance during the match.

Non-matching categories

Optional

 NON_MATCHING_CATEGORIES

[vector: table]

Default: [Skip output]

 Output table for categories which do not match any symbol in the database. :ref:`One of <output_parameter_widget>`:

Non-matching symbol names

Optional

 NON_MATCHING_SYMBOLS

[vector: table]

Default: [Skip output]

 Output table for symbols from the provided style database which do not match any category. :ref:`One of <output_parameter_widget>`:

Outputs

Label Name Type Description
Non-matching categories NON_MATCHING_CATEGORIES [vector: table] Lists categories which could not be matched to any symbol in the provided style database
Non-matching symbol names NON_MATCHING_SYMBOLS [vector: table] Lists symbols from the provided style database which could not match any category
Categorized layer OUTPUT [same as input] The input vector layer with the categorized style applied. No new layer is output.

Python code

Algorithm ID: native:categorizeusingstyle

Create style database from project

Extracts all style objects (symbols, color ramps, text formats and label settings) from a QGIS project.

The extracted symbols are saved to a QGIS style database (:file:`XML` format), which can be managed and imported via the :ref:`Style Manager <vector_style_manager>` dialog.

.. seealso:: :ref:`qgiscombinestyles`

Parameters

Label Name Type Description

Input project (leave blank to use current)

Optional

 INPUT [file] A QGIS project file to extract the style items from
Objects to extract OBJECTS [enumeration] [list]

Types of style items in the input project you would like to put in the new database. These can be:
Output style database OUTPUT

[file]

Default: [Save to temporary file]

 Specify the output :file:`.XML` file for the selected style items. :ref:`One of <output_parameter_widget>`:

Outputs

Label Name Type Description
Color ramp count COLORRAMPS [numeric: integer] Number of color ramps
Label settings count LABELSETTINGS [numeric: integer] Number of label settings
Output style database OUTPUT [file] Output :file:`.XML` file for the selected style items
Symbol count SYMBOLS [numeric: integer] Number of symbols
Text format count TEXTFORMATS [numeric: integer] Number of text formats

Python code

Algorithm ID: native:stylefromproject

Export atlas layout as image

Exports the atlas of a print layout as image files (e.g. PNG or JPEG images).

If a coverage layer is set, the selected layout's atlas settings exposed in this algorithm will be overwritten. In this case, an empty filter or sort by expression will turn those settings off.

Parameters

Basic parameters

Label Name Type Description
Atlas layout LAYOUT [layout] Layout to export

Coverage layer

Optional

 COVERAGE_LAYER [vector: geometry] Layer to use to generate the atlas
Filter expression FILTER_EXPRESSION [expression] Expression to use to filter out atlas features

Sort expression

Optional

 SORTBY_EXPRESSION [expression] Expression to use to sort the atlas features
Reverse sort order SORTBY_REVERSE

[boolean]

Default: False

 Determines if sorting should be inverted. Used when a sort expression is provided.
Output filename expression FILENAME_EXPRESSION

[expression]

Default: 'output_'||@atlas_featurenumber

 Expression for use to generate filenames
Output folder FOLDER [folder] Destination folder where the images will be generated

Advanced parameters

Label Name Type Description

Map layers to assign to unlocked map item(s)

Optional

 LAYERS [enumeration] [layer] Layers to display in the map item(s) whose contents are not locked
Image format EXTENSION

[enumeration]

Default: png

 File format of the generated output(s). The list of available formats varies depending on OS and installed drivers.

DPI

Optional

DPI

Default: Not set

 [numeric: double] DPI of the output file(s). If not set, the value in the print layout settings will be used.
Generate world file GEOREFERENCE

[boolean]

Default: True

 Determines if a world file should be generated
Export RDF metadata INCLUDE_METADATA

[boolean]

Default: True

 Determines if RDF metadata (title, author, ...) should be generated
Enable antialiasing ANTIALIAS

[boolean]

Default: True

 Determines if antialiasing should be enabled

Outputs

Label Name Type Description
Image file OUTPUT [file] Image files generated by the atlas layout

Python code

Algorithm ID: native:atlaslayouttoimage

Export atlas layout as PDF (multiple files)

Exports the atlas of a print layout to multiple PDF files.

If a coverage layer is set, the selected layout's atlas settings exposed in this algorithm will be overwritten. In this case, an empty filter or sort by expression will turn those settings off.

Parameters

Basic parameters

Label Name Type Description
Atlas layout LAYOUT [layout] Layout to export

Coverage layer

Optional

 COVERAGE_LAYER [vector: geometry] Layer to use to generate the atlas
Filter expression FILTER_EXPRESSION [expression] Expression to use to filter out atlas features

Sort expression

Optional

 SORTBY_EXPRESSION [expression] Expression to use to sort the atlas features
Reverse sort order SORTBY_REVERSE

[boolean]

Default: False

 Determines if sorting should be inverted. Used when a sort expression is provided.

Output filename

Optional

 OUTPUT_FILENAME [expression] Name pattern of the PDF output files.
Output folder OUTPUT_FOLDER [folder] Destination folder for the output PDF files.

Advanced parameters

Label Name Type Description

Map layers to assign to unlocked map item(s)

Optional

 LAYERS [enumeration] [layer] Layers to display in the map item(s) whose contents are not locked

DPI

Optional

DPI

Default: Not set

 [numeric: double] DPI of the output file(s). If not set, the value in the print layout settings will be used.
Always export as vectors FORCE_VECTOR

[boolean]

Default: False

 Determines if vectorial data should be left as vectors
Always export as raster FORCE_RASTER

[boolean]

Default: False

 Forces all the items in the map to be rasterized. This parameter takes precedence over the FORCE_VECTOR parameter.
Append georeference information GEOREFERENCE

[boolean]

Default: True

 Determines if a world file should be generated
Export RDF metadata INCLUDE_METADATA

[boolean]

Default: True

 Determines if RDF metadata (title, author, ...) should be generated
Disable tiled raster layer exports DISABLE_TILED

[boolean]

Default: False

 Determines if raster should be tiled
Simplify geometries to reduce output file size SIMPLIFY

[boolean]

Default: True

 Determines if geometries should be simplified to reduce output file size
Text export TEXT_FORMAT

[enumeration]

Default: 0

Determines if text should be exported as path or text objects. :ref:`Possible options <render_labels_text>` are:

  • 0 - Always export text as paths (recommended)
  • 1 - Always export texts as text objects
  • 2 - Prefer exporting texts as text objects --- Added in 3.40
Image compression IMAGE_COMPRESSION

[enumeration]

Default: 0

Determines compression level of the image and how suitable the file could be for printing outputs or post-production in external applications. Possible options are:

  • 0 - Lossy (JPEG)
  • 1 - Lossless

Outputs

Label Name Type Description
PDF file OUTPUT [file] PDF file corresponding to the exported atlas layout

Python code

Algorithm ID: native:atlaslayouttomultiplepdf

Export atlas layout as PDF (single file)

Exports the atlas of a print layout as a single PDF file.

If a coverage layer is set, the selected layout's atlas settings exposed in this algorithm will be overwritten. In this case, an empty filter or sort by expression will turn those settings off.

Parameters

Basic parameters

Label Name Type Description
Atlas layout LAYOUT [layout] Layout to export

Coverage layer

Optional

 COVERAGE_LAYER [vector: geometry] Layer to use to generate the atlas
Filter expression FILTER_EXPRESSION [expression] Expression to use to filter out atlas features

Sort expression

Optional

 SORTBY_EXPRESSION [expression] Expression to use to sort the atlas features
Reverse sort order SORTBY_REVERSE

[boolean]

Default: False

 Determines if sorting should be inverted. Used when a sort expression is provided.
PDF file OUTPUT

[file]

Default: [Save to temporary file]

 Name (including path) of the output file. :ref:`One of <output_parameter_widget>`:

Advanced parameters

Label Name Type Description

Map layers to assign to unlocked map item(s)

Optional

 LAYERS [enumeration] [layer] Layers to display in the map item(s) whose contents are not locked

DPI

Optional

DPI

Default: Not set

 [numeric: double] DPI of the output file(s). If not set, the value in the print layout settings will be used.
Always export as vectors FORCE_VECTOR

[boolean]

Default: False

 Determines if vectorial data should be left as vectors
Always export as raster FORCE_RASTER

[boolean]

Default: False

 Forces all the items in the map to be rasterized. This parameter takes precedence over the FORCE_VECTOR parameter.
Append georeference information GEOREFERENCE

[boolean]

Default: True

 Determines if a world file should be generated
Export RDF metadata INCLUDE_METADATA

[boolean]

Default: True

 Determines if RDF metadata (title, author, ...) should be generated
Disable tiled raster layer exports DISABLE_TILED

[boolean]

Default: False

 Determines if raster should be tiled
Simplify geometries to reduce output file size SIMPLIFY

[boolean]

Default: True

 Determines if geometries should be simplified to reduce output file size
Text export TEXT_FORMAT

[enumeration]

Default: 0

Determines if text should be exported as path or text objects. :ref:`Possible options <render_labels_text>` are:

  • 0 - Always export text as paths (recommended)
  • 1 - Always export texts as text objects
  • 2 - Prefer exporting texts as text objects --- Added in 3.40
Image compression IMAGE_COMPRESSION

[enumeration]

Default: 0

Determines compression level of the image and how suitable the file could be for printing outputs or post-production in external applications. Possible options are:

  • 0 - Lossy (JPEG)
  • 1 - Lossless

Outputs

Label Name Type Description
PDF file OUTPUT [file] PDF file corresponding to the exported atlas layout

Python code

Algorithm ID: native:atlaslayouttopdf

Export print layout as image

Exports a print layout as an image file (e.g. PNG or JPEG images)

Parameters

Basic parameters

Label Name Type Description
Print layout LAYOUT [layout] Layout to export
Image file OUTPUT

[file]

Default: [Save to temporary file]

 Name (including path) of the output file. :ref:`One of <output_parameter_widget>`:

Advanced parameters

Label Name Type Description

Map layers to assign to unlocked map item(s)

Optional

 LAYERS [enumeration] [layer] Layers to display in the map item(s) whose contents are not locked

DPI

Optional

DPI

Default: Not set

 [numeric: double] DPI of the output file(s). If not set, the value in the print layout settings will be used.
Generate world file GEOREFERENCE

[boolean]

Default: True

 Determines if a world file should be generated
Export RDF metadata INCLUDE_METADATA

[boolean]

Default: True

 Determines if RDF metadata (title, author, ...) should be generated
Enable antialiasing ANTIALIAS

[boolean]

Default: True

 Determines if antialiasing should be enabled

Outputs

Label Name Type Description
Image file OUTPUT [file] Image file corresponding to the exported print layout

Python code

Algorithm ID: native:printlayouttoimage

Export print layout as PDF

Exports a print layout as a PDF file.

Parameters

Basic parameters

Label Name Type Description
Print Layout LAYOUT [layout] Layout to export
PDF file OUTPUT

[file]

Default: [Save to temporary file]

 Name (including path) of the output file. :ref:`One of <output_parameter_widget>`:

Advanced parameters

Label Name Type Description

Map layers to assign to unlocked map item(s)

Optional

 LAYERS [enumeration] [layer] Layers to display in the map item(s) whose contents are not locked

DPI

Optional

DPI

Default: Not set

 [numeric: double] DPI of the output file(s). If not set, the value in the print layout settings will be used.
Always export as vectors FORCE_VECTOR

[boolean]

Default: False

 Determines if vectorial data should be left as vectors
Always export as raster FORCE_RASTER

[boolean]

Default: False

 Forces all the items in the map to be rasterized. This parameter takes precedence over the FORCE_VECTOR parameter.
Append georeference information GEOREFERENCE

[boolean]

Default: True

 Determines if a world file should be generated
Export RDF metadata INCLUDE_METADATA

[boolean]

Default: True

 Determines if RDF metadata (title, author, ...) should be generated
Disable tiled raster layer exports DISABLE_TILED

[boolean]

Default: False

 Determines if raster should be tiled
Simplify geometries to reduce output file size SIMPLIFY

[boolean]

Default: True

 Determines if geometries should be simplified to reduce output file size
Text export TEXT_FORMAT

[enumeration]

Default: 0

Determines if text should be exported as path or text objects. :ref:`Possible options <render_labels_text>` are:

  • 0 - Always export text as paths (recommended)
  • 1 - Always export texts as text objects
  • 2 - Prefer exporting texts as text objects --- Added in 3.40
Image compression IMAGE_COMPRESSION

[enumeration]

Default: 0

Determines compression level of the image and how suitable the file could be for printing outputs or post-production in external applications. Possible options are:

  • 0 - Lossy (JPEG)
  • 1 - Lossless
Export layers as separate PDF files SEPARATE_LAYERS

[boolean]

Default: False

 If True, then a separate PDF file will be created per layer per map item in the layout. Additionally, separate PDF files may be created for other complex layout items, resulting in a set of PDF files which contain logical atomic components of the layout.

Outputs

Label Name Type Description
PDF file OUTPUT [file] PDF file(s) corresponding to the exported print layout

Python code

Algorithm ID: native:printlayouttopdf

Extract labels

Extracts label information from a rendered map at a given extent and scale.

If a map theme is provided, the rendered map will match the visibility and symbology of that theme. If left blank, all visible layers from the project will be used. Extracted label information include: position (served as point geometries), the associated layer name and feature ID, label text, rotation (in degree, clockwise), multiline alignment, and font details.

Warning

This algorithm drops existing primary keys or FID values and regenerates them in output layers.

Parameters

Basic parameters

Label Name Type Description
Map extent EXTENT [extent] Extent of the map to extract the labels from
Map scale SCALE [scale] Extracted labels will be rendered using their properties set at this scale.

Map theme

Optional

 MAP_THEME [maptheme] A map theme displaying the layers to extract the labels from. If unset, labels of the currently visible layers are extracted.
Include unplaced labels INCLUDE_UNPLACED

[boolean]

Default: True

 Specify whether all overlapping labels should be extracted, including the conflicting (thus unplaced) ones.
Extracted labels OUTPUT

[vector: point]

Default: [Create temporary layer]

 Specify the output vector layer for the extent(s). :ref:`One of <output_parameter_widget>`:

Advanced parameters

Label Name Type Description

Map resolution (in DPI)

Optional

DPI

Default: 96.0

 [numeric: double]  

Outputs

Label Name Type Description
Extracted labels OUTPUT [vector: point]

Point vector layer representing the fetched labels. Each feature has attributes identifying its source (layer, feature ID) and the assigned labeling properties (text, font, size, rotation, ...). A default style with labeling and null symbol is also applied to the layer.

Warning

Because some of the generated fields have name with more than 10 characters, using the ESRI shapefile format (:file:`.SHP`) to store the output may lead to unexpected rendering while loading the layer in QGIS.

Python code

Algorithm ID: native:extractlabels

Print layout map extent to layer

Creates a polygon layer containing the extent of a print layout map item (or items), with attributes specifying the map size (in layout units, i.e. the :ref:`reference map <reference_map>` units), scale and rotation.

If the map item parameter is specified, then only the matching map extent will be exported. If it is not specified, all map extents from the layout will be exported.

Optionally, a specific output CRS can be specified. If it is not specified, the original map item CRS will be used.

Parameters

Basic parameters

Label Name Type Description
Print layout LAYOUT [enumeration] A print layout in the current project

Map item

Optional

 MAP

[enumeration]

Default: All the map items

 The map item(s) whose information you want to extract. If none is provided then all the map items are processed.
Extent OUTPUT

[vector: polygon]

Default: [Create temporary layer]

 Specify the output vector layer for the extent(s). :ref:`One of <output_parameter_widget>`:

Advanced parameters

Label Name Type Description

Override CRS

Optional

 CRS

[crs]

Default: The layout CRS

 Select the CRS for the layer in which the information will be reported.

Outputs

Label Name Type Description
Map height HEIGHT [numeric: double]  
Extent OUTPUT [vector: polygon] Output polygon vector layer containing extents of all the input layout map item(s)
Map rotation ROTATION [numeric: double]  
Map scale SCALE [numeric: double]  
Map width WIDTH [numeric: double]  

Python code

Algorithm ID: native:printlayoutmapextenttolayer

Set layer style

Applies a provided style to a layer. The style must be defined in a :file:`QML` file.

No new output are created: the style is immediately assigned to the layer.

Parameters

Label Name Type Description
Input Layer INPUT [layer] Input layer you want to apply the style to
Style file STYLE [file] Path to the .qml file of the style

Outputs

Label Name Type Description
  OUTPUT [same as input] The input layer with the new style assigned. No new layer is created.

Python code

Algorithm ID: native:setlayerstyle

Topological coloring

Assigns a color index to polygon features in such a way that no adjacent polygons share the same color index, whilst minimizing the number of colors required.

The algorithm allows choice of method to use when assigning colors.

A minimum number of colors can be specified if desired. The color index is saved to a new attribute named color_id.

The following example shows the algorithm with four different colors chosen; as you can see each color class has the same amount of features.

img/topological_color.png

Topological colors example

Parameters

Label Name Type Description
Input layer INPUT [vector: polygon] The input polygon layer
Minimum number of colors MIN_COLORS

[numeric: integer]

Default: 4

 The minimum number of colors to assign. Minimum 1, maximum 1000.
Minimum distance between features MIN_DISTANCE

[numeric: double]

Default: 0.0

 Prevent nearby (but non-touching) features from being assigned equal colors. Minimum 0.0.
Balance color assignment BALANCE

[enumeration]

Default: 0

Options are:

  • 0 --- By feature count

    Attempts to assign colors so that the count of features assigned to each individual color index is balanced.

  • 1 --- By assigned area

    Assigns colors so that the total area of features assigned to each color is balanced. This mode can be useful to help avoid large features resulting in one of the colors appearing more dominant on a colored map.

  • 2 --- By distance between colors

    Assigns colors in order to maximize the distance between features of the same color. This mode helps to create a more uniform distribution of colors across a map.
Colored OUTPUT

[vector: polygon]

Default: [Create temporary layer]

 Specify the output layer. :ref:`One of <output_parameter_widget>`:

Outputs

Label Name Type Description
Colored OUTPUT [vector: polygon] Polygon vector layer with an added color_id column

Python code

Algorithm ID: qgis:topologicalcoloring

Transfer annotations from main layer

Transfers all :ref:`annotations <annotation_layer>` from the main annotation layer in a project to a new annotation layer. Items placement can then be adjusted within the layer stack.

Parameters

Label Name Type Description
New layer name LAYER_NAME

[string]

Default: 'Annotations'

 Name of the annotations layer to create

Outputs

Label Name Type Description
New layer name OUTPUT [layer] A layer with items from the main annotation layer

Python code

Algorithm ID: native:transferannotationsfrommain