The Sparse Image Format (SIF) is a file format for storing raster images with sparse pixel data. Images are broken down into a grid of tiles of fixed size. A tile is only stored in a file if any two pixels in it are different. This is particularly useful for images that are highly homogeneous in color. A few applications of SIF include using it to store:

• land-cover classifications
• training data for pixel classifiers
• sparse overlay rasters over large images

SIF is not intended for space-efficiently storing multispectral imagery or photos. A C library is provided for manipulating SIF files.