Creating an Output¶

Export as Image¶

Clicking the ^{Export as image} icon will ask you to enter the filename to use to export composition: in case of multi-page composition, each page will be exported to a file with the given name appended with the page number.

You can then override the print resolution (set in Composition tab) and resize exported image dimensions.

By checking Crop to content option, the images output by composer will include only the area of the composition with content. There’s also an option for margins to add around the item bounds if required.

If the composition includes a single page, then the output will be sized to include EVERYTHING on the composition. If it’s a multi-page composition, then each page will be cropped to only include the area of that page with items.

Figure Composer Output 2:

Image Export Options

If you need to export your layout as a georeferenced image (e.g., to share with other projects), you need to enable this feature under the Composition tab. Check World file on and choose the map item to use. With this option, the ‘Export as image’ action will create a world file along the exported image.

Export as SVG¶

With ^{Export as SVG}, you also need to fill the filename (used as a basename for all files in case of multi_page composition) and then can apply Crop to content option.

The SVG export options dialog allows also to :

• export map layers as svg groups:
• render map labels as outlines

Figure Composer Output 3:

SVG Export Options

Export as PDF¶

The ^{Export as PDF} exports all the composition into a single PDF file.

If you applied to your composition or any shown layer an advanced effect such as blend modes, transparency or symbol effects, these cannot be printed as vectors and your effects may be lost. Checking Print as a raster in Composition tab helps to keep the effects but rasterize the composition. Note that the Force layer to render as raster in the Rendering tab of Layer Properties is a layer-level alternative that avoids global composition rasterization.

Generate an Atlas¶

The Print Composer includes generation functions that allow you to create map books in an automated way. The concept is to use a coverage layer, which contains geometries and fields. For each geometry in the coverage layer, a new output will be generated where the content of some canvas maps will be moved to highlight the current geometry. Fields associated with this geometry can be used within text labels.

Every page will be generated with each feature. To enable the generation of an atlas and access generation parameters, refer to the Atlas generation tab. This tab contains the following widgets (see figure_composer_atlas_1):

Figure Composer Atlas 1:

Atlas generation tab

• Generate an atlas, which enables or disables the atlas generation.
• A Coverage layer combo box that allows you to choose the (vector) layer containing the features on which to iterate over.
• An optional Hidden coverage layer that, if checked, will hide the coverage layer (but not the other ones) during the generation.
• An optional Page name combo box to give a more explicit name to each feature page(s) when previewing atlas. You can select an attribute of the coverage layer or set an expression. If this option is empty, QGIS will use an internal ID, according to the filter and/or the sort order applied to the layer.
• An optional Filter with text area that allows you to specify an expression for filtering features from the coverage layer. If the expression is not empty, only features that evaluate to True will be selected. The button on the right allows you to display the expression builder.
• An optional Sort by that, if checked, allows you to sort features of the coverage layer. The associated combo box allows you to choose which column will be used as the sorting key. Sort order (either ascending or descending) is set by a two-state button that displays an up or a down arrow.

You also have options to set the output of the atlas:

• An Output filename expression textbox that is used to generate a filename for each geometry if needed. It is based on expressions. This field is meaningful only for rendering to multiple files.
• A Single file export when possible that allows you to force the generation of a single file if this is possible with the chosen output format (PDF, for instance). If this field is checked, the value of the Output filename expression field is meaningless.

You can use multiple map items with the atlas generation; each map will be rendered according to the coverage features. To enable atlas generation for a specific map item, you need to check Controlled by Atlas under the item properties of the map item. Once checked, you can set:

• A Margin around feature that allows you to select the amount of space added around each geometry within the allocated map. Its value is meaningful only when using the auto-scaling mode.
• A Predefined scale (best fit). It will use the best fitting option from the list of predefined scales in your project properties settings (see Project –> Project Properties –> General –> Project Scales to configure these predefined scales).
• A Fixed scale that allows you to toggle between auto-scale and fixed-scale mode. In fixed-scale mode, the map will only be translated for each geometry to be centered. In auto-scale mode, the map’s extents are computed in such a way that each geometry will appear in its entirety.

The area of [% upper(CITY_NAME) || ',' || ZIPCODE || ' is '
format_number($area/1000000,2) %] km2

The area of [% upper(CITY_NAME)%],[%ZIPCODE%] is
[%format_number($area/1000000,2) %] km2

The area of PARIS,75001 is 1.94 km2

CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry)
THEN 'Landscape' ELSE 'Portrait' END

(CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry)
THEN 297 ELSE 210 END) - 20

(CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry)
THEN 210 ELSE 297 END) - 20

(CASE WHEN bounds_width($atlasgeometry) > bounds_height($atlasgeometry)
THEN 297 ELSE 210 END) / 2

Preview and generate¶

Figure Composer Atlas 2:

Atlas Preview toolbar

Once the atlas settings have been configured and composer items (map, table, image...) linked to it, you can create a preview of all the pages by clicking Atlas ‣ Preview Atlas or ^{Preview Atlas} icon. You can then use the arrows in the same toolbar to navigate through all the features:

• ^{First feature}
• ^{Previous feature}
• ^{Next feature}
• ^{Last feature}

You can also use the combo box to directly select and preview a specific feature. The combo box shows atlas features name according to the expression set in the atlas Page name option.

As for simple compositions, an atlas can be generated in different ways (see Creating an Output for more information). Instead of Composer menu, rather use tools from Atlas menu or Atlas toolbar.

This means that you can directly print your compositions with Atlas ‣ Print Atlas. You can also create a PDF using Atlas ‣ Export Atlas as PDF...: The user will be asked for a directory to save all the generated PDF files, except if the Single file export when possible has been selected. In that case, you’ll be prompted to give a filename.

With Atlas ‣ Export Atlas as Images... or Atlas ‣ Export Atlas as SVG... tool, you’re also prompted to select a folder. Each page of each atlas feature composition is exported to an image or SVG file.

Совет

Print a specific atlas feature

If you want to print or export the composition of only one feature of the atlas, simply start the preview, select the desired feature in the drop-down list and click on Composer ‣ Print (or export... to any supported file format).