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 the Map Composer

The QGIS Map Composer allows you to combine a map with nonspatial elements that enhance the understanding of the map. In this recipe, we'll create a basic map composition. A composition requires you to define a physical paper size and output format. Even a simple composition example such as this has over 20 lines of configuration options.

Getting ready

You will need to download the following zipped shapefile and extract it to your qgis_data directory in a subdirectory named hancock:

You will also need to open the Python Console under the Plugins menu in QGIS. You can run this recipe in the console, or wrap it in a script for the Script Runner plugin using the template provided with the plugin.

How to do it...

In this recipe, the major steps are to load the shapefile into a map, build the map composition, and render it to an image, as follows:

  1. First, we need to import the Qt libraries for image handling: