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

Converting a TIFF image to a JPEG image

Image format conversion is a part of nearly every geospatial project. Rasters come in dozens of different specialized formats, making conversion to a more common format a necessity. The GDAL utilities include a tool called gdal_translate specifically for format conversion. Unfortunately, the algorithm in the Processing Toolbox is limited in functionality. For format conversion, it is easier to use the core GDAL API.

Getting ready

We will use the SatImage raster available at

Place this raster in your /qgis_data/rasters directory.

How to do it...

In this recipe, we'll open a TIFF image using GDAL and copy it to a new dataset as a JPEG2000 image, which allows you to use the JPEG format while maintaining geospatial information. To do this, we need to perform the following steps:

  1. Start QGIS.

  2. From the Plugins menu, select Python Console.

  3. Import the gdal module:

            from osgeo import gdal 
  4. Get...