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 raster footprints

A common way to catalog the raster datasets that consist of a large number of files is by creating a vector dataset with polygon footprints of the extent of each raster file. The vector footprint files can be easily loaded in QGIS or served over the Web. This recipe demonstrates a method to create a footprint vector from a directory full of raster files. We will build this program as a Processing Toolbox script, which is easier to build than a QGIS plugin and provides both a GUI and a clean programming API.

Getting ready

Download the sample raster image scenes from Unzip the scenes directory into a directory named rasters in your qgis_data directory.

For this recipe, we will create a new Processing Toolbox script using the following steps:

  1. In the QGIS Processing Toolbox, expand the Scripts tree menu.

  2. Next, expand the Tools tree menu.

  3. Finally, double-click on the Create new script item to bring up the processing...