23.1.1. Cartography

23.1.1.1. 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.

See also

Create style database from project

23.1.1.1.1. 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: 0 — Symbols 1 — Color ramps 2 — Text formats 3 — Label settings
Output style database	OUTPUT	[file] Default: [Save to temporary file]	Output .XML file combining the selected style items. One of: Save to a Temporary Layer (TEMPORARY_OUTPUT) Save to File… The file encoding can also be changed here.

23.1.1.1.2. Outputs

Label	Name	Type	Description
Color ramp count	COLORRAMPS	[number]
Label settings count	LABELSETTINGS	[number]
Output style database	OUTPUT	[file]	Output .XML file combining the selected style items
Symbol count	SYMBOLS	[number]
Text format count	TEXTFORMATS	[number]

23.1.1.1.3. Python code

Algorithm ID: qgis:combinestyles

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.

23.1.1.2. 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 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.

23.1.1.2.1. 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 (.XML) containing the symbols to apply to the input layer categories. The file can be obtained from the Style Manager 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	[table] Default: [Skip output]	Output table for categories which do not match any symbol in the database. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.
Non-matching symbol names Optional	NON_MATCHING_SYMBOLS	[table] Default: [Skip output]	Output table for symbols from the provided style database which do not match any category. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.1.2.2. Outputs

Label	Name	Type	Description
Non-matching categories	NON_MATCHING_CATEGORIES	[table]	Lists categories which could not be matched to any symbol in the provided style database
Non-matching symbol names	NON_MATCHING_SYMBOLS	[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.

23.1.1.2.3. Python code

Algorithm ID: qgis:categorizeusingstyle

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.

23.1.1.3. 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 (XML format), which can be managed and imported via the Style Manager dialog.

See also

Combine style databases

23.1.1.3.1. 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: 0 — Symbols 1 — Color ramps 2 — Text formats 3 — Label settings
Output style database	OUTPUT	[file] Default: [Save to temporary file]	Specify the output .XML file for the selected style items. One of: Save to a Temporary Layer (TEMPORARY_OUTPUT) Save to File… The file encoding can also be changed here.

23.1.1.3.2. Outputs

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

23.1.1.3.3. Python code

Algorithm ID: qgis:stylefromproject

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.

23.1.1.4. 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 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.

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.
Overrride CRS Optional	CRS	[crs] Default: The layout CRS	Select the CRS for the layer in which the information will be reported.
Extent	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output vector layer for the extent(s). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.1.4.1. Outputs

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

23.1.1.4.2. Python code

Algorithm ID: qgis:printlayoutmapextenttolayer

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.

23.1.1.5. 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.

Fig. 23.1 Topological colors example

23.1.1.5.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	The input polygon layer
Minimum number of colors	MIN_COLORS	[number] Default: 4	The minimum number of colors to assign. Minimum 1, maximum 1000.
Minimum distance between features	MIN_DISTANCE	[number] 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. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.1.5.2. Outputs

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

23.1.1.5.3. Python code

Algorithm ID: qgis:topologicalcoloring

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.