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 a 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://github.com/GeospatialPython/Learn/raw/master/dem.zip, which you can unzip to 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:

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

           from PyQt4 import QtGui 
   

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

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

3. Now, we create a...