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

Creating the simplest map renderer

In order to turn a dynamic GIS map into a static map image or document, you must create a renderer to freeze the map view and create a graphic version of it. In this recipe, we'll render a map to a JPEG image and save it.

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 these lines of code inside the console.

How to do it...

In this recipe, we will load our shapefile, add it to the map, create a blank image, set up the map view, render the map image, and save it. To do this, we need to perform the following steps:

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

            from PyQt4.QtGui import * 
            from PyQt4.QtCore import * 
  2. Next, we load the layer and add it to...