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How is the map renderer used in QGIS?
In the code we expect we are running within QGIS application and thus use the map renderer from map canvas. The composition uses various parameters from the map renderer, most importantly the default set of map layers and the current extent.
What’s the best way to ask a QGIS question?
Asking for help, clarification, or responding to other answers. Making statements based on opinion; back them up with references or personal experience. To learn more, see our tips on writing great answers. Browse other questions tagged qgis pyqgis or ask your own question.
How to render layers using qgsmaprenderer in Photoshop?
Render some layers using QgsMapRenderer — create destination paint device ( QImage, QPainter etc.), set up layer set, extent, output size and do the rendering
Is there a GUI library for QGIS composer?
QGIS application has a convenient GUI for placement of the elements, though it is not available in the GUI library. If you are not familiar with Qt Graphics View framework , then you are encouraged to check the documentation now, because the composer is based on it.
How to define the extent of a QGIS map?
Currently I am just using the simple rendering technique outlined here: http://www.qgis.org/pyqgis-cookbook/composer.html#simple-rendering I have failed, however, at adapting this code to define a specific extent. I provide the code below. The only examples that I can find that show how to change extent involve creating a MapCanvas.
Is there a GUI for the QGIS application?
QGIS application has a convenient GUI for placement of the elements, though it is not available in the GUI library. If you are not familiar with Qt Graphics View framework , then you are encouraged to check the documentation now, because the composer is based on it. Also check the Python documentation of the implementation of QGraphicView.
How to create a spatial index in QGIS?
If not, then try to create a spatial index to your data. The spatial index can improve the speed of rendering your data in QGIS. To create spatial index, go to layer properties -> General tab -> Create Spatial Index, as you can see below: You can create spatial index directly from OSGEO4W Shell by adding the following command:
What to do about QGIS rendering performance bottleneck?
Using a nation-wide road network classified by “type” (5 values) but displaying a dozen street segments, it is instantaneous when all feature types are displayed and takes a couple of seconds should they are filtered. –> if it is enabled, try disabling it to improve performances.
Is there support for composer templates in QGIS?
Besides creating the composer items by hand, QGIS has support for composer templates which are essentially compositions with all their items saved to a .qpt file (with XML syntax). Unfortunately this functionality is not yet available in the API.
Can a composer be used to print a map?
Using the composer it is possible to create complex map layouts consisting of map views, labels, legend, tables and other elements that are usually present on paper maps. The layouts can be then exported to PDF, raster images or directly printed on a printer. The composer consists of a bunch of classes. They all belong to the core library.