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

Using SVG for layer symbols

Scalable Vector Graphics (SVG) are an XML standard that defines vector graphics which can be scaled at any resolution. QGIS can use SVG files as markers for points. In this recipe, we'll use Python to apply one of the SVG symbols included with QGIS to a point layer.

Getting ready

For this recipe, download the following zipped point shapefile layer from

Extract it to your qgis_data directory.

How to do it...

In the following steps, we'll load the vector layer, build a symbol layer and renderer, and add it to the layer, as follows:

  1. First, we'll define the path to the shapefile:

            src = "/qgis_data/NYC_MUSEUMS_GEO/NYC_MUSEUMS_GEO.shp" 
  2. Next, we'll load the layer:

            lyr = QgsVectorLayer(src, "Museums", "ogr") 
  3. Now, we define the properties of the symbol, including the location of the SVG file as a Python dictionary:

            svgStyle = {} 
            svgStyle['fill'] = '#0000ff...