Rendering a single band raster using a color ramp algorithm

A color ramp allows you to render a raster using just a few colors to represent different ranges of cell values that have similar meaning, in order to group them. The approach that will be used in this recipe is the most common way to render elevation data.

Getting ready

You can download a sample DEM from https://geospatialpython.googlecode.com/files/dem.zip, which you can unzip in a directory named rasters in your qgis_data directory.

How to do it...

In the following steps, we will set up objects to color a raster, create a list establishing the color ramp ranges, apply the ramp to the layer renderer, and finally add the layer to the map. To do this, we need to perform the following steps:

1. First, we import the QtGui library for color objects in the QGIS Python Console:

   from PyQt4 import QtGui
   

2. Next, we load the raster layer, as follows:

   lyr = QgsRasterLayer("/Users/joellawhead/qgis_data/rasters/dem.asc", "DEM")
   

3. Now, we create a generic...