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 a mouse coordinate tracking tool

In this recipe, we'll build a tool that tracks and displays the mouse coordinates in real time. This tool will also demonstrate how to interact with the status bar of a QGIS application.

Getting ready

We will use the application framework from the Adding standard map tools to the canvas recipe, so complete that recipe. We will extend that application with the coordinate tracking tool. A complete version of this application is available in the code samples provided with this book. It will also be beneficial to study the other two tool-related recipes in this chapter, Using a map tool to draw polygons or lines on the canvas and Using a map tool to draw points on the canvas, as this recipe builds on them as well.

How to do it...

We will add an event filter to the basic standalone QGIS application and use it to grab the current mouse coordinates as well as update the status bar. To do this, we need to perform the following steps:

  1. At the last line of our application...