Creating pyramids for a raster

Pyramids, or overview images, sacrifice the disk space for map rendering speed by storing resampled, lower-resolution versions of images in the file alongside the full resolution image. Once you have finalized a raster, building pyramid overviews is a good idea.

Getting ready

For this recipe, we will use a false-color image, that you can download from https://geospatialpython.googlecode.com/files/FalseColor.zip.

Unzip this TIF file and place it in your /qgis_data/rasters directory.

How to do it...

The Processing Toolbox has a dedicated algorithm for building pyramid images. Perform the following steps to create pyramids for a raster

1. Start QGIS.

2. From the Plugins menu, select Python Console.

3. Import the processing module:

   import processing
   

4. Run the gdalogr:overviews algorithm, specifying the process name, input image, overview levels, the option to remove existing overviews, resampling method (0 is the nearest neighbor), and overview format (1 is internal):

   processing.runalg...