Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By : Joel Lawhead
Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By: Joel Lawhead

Overview of this book

QGIS is a desktop geographic information system that facilitates data viewing, editing, and analysis. Paired with the most efficient scripting language—Python, we can write effective scripts that extend the core functionality of QGIS. Based on version QGIS 2.18, this book will teach you how to write Python code that works with spatial data to automate geoprocessing tasks in QGIS. It will cover topics such as querying and editing vector data and using raster data. You will also learn to create, edit, and optimize a vector layer for faster queries, reproject a vector layer, reduce the number of vertices in a vector layer without losing critical data, and convert a raster to a vector. Following this, you will work through recipes that will help you compose static maps, create heavily customized maps, and add specialized labels and annotations. As well as this, we’ll also share a few tips and tricks based on different aspects of QGIS.
Table of Contents (16 chapters)
QGIS Python Programming Cookbook - Second Edition
About the Author
About the Reviewer
Customer Feedback

Using live layer effects

Live layer effects provide advanced cartographic effects for QGIS maps. These drawing effects go beyond the traditional GIS maps into the realm of map illustrations to add pleasing visualizations, including blur effects, inner and outer glows, and drop shadows. In this recipe, we'll add the inner glow and drop shadow live layer effects to a polygon layer.

Getting ready

Download the following zipped shapefile and extract it to a directory named ms in your qgis_data directory:

How to do it...

We will create a layer based on the shapefile. Then we'll build three symbol layers for the base fill color, the inner glow, and the drop shadow. We'll add those symbol layers to the layer's base symbol and finally, add the layer to the map:

  1. First, we need to import the PyQt GUI library to handle color objects:

            from PyQt4.QtGui import * 
  2. Next, we'll create the shapefile layer:

            lyr = QgsVectorLayer...