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

Loading a raster layer

The QGSRasterLayer API provides a convenient, high-level interface to raster data. To use this interface, we must load a layer into QGIS. The API allows you to work with a layer without adding it to the map. In this way, we'll load a layer and then add it to the map.

Getting ready

As with the other recipes in this book, you need to create a directory called qgis_data in our root or user directory, which provides a short path name without spaces. This setup will help prevent any frustrating errors that result from path-related issues on a given system. In this recipe, and the others, we'll use a Landsat satellite image of the Mississippi Gulf Coast, which you can download from

Unzip the SatImage.tif and SatImage.tfw files and place them in a directory named rasters within your qgis_data directory.

How to do it...

Now we'll go through how to load a raster layer and then add it step by step to the map:

  1. Start...