GDAL Dataset and Band abstraction for simple tiled raster calculations (AKA "map algebra").
Can handle rasters with different extents and coordinate systems as long as they overlap.
Cellsizes must be the same.

This gist contains 3 scripts: 
  - The command line raster calculator "gdal_calculator.py".  This is only for command line use, it can not be imported.
  - The raster calculations module "gdal_dataset.py". This is where it all happens! This module can be imported and used in your own scripts
  - A helper module "geometry.py"