A method according to the invention conserves host system resources by compressing an image region according to the type of graphics command used to generate or modify the region. As an image is being rendered, a list of modified image regions is maintained. For each modified image region, metadata are associated with the region to identify the type of graphics command that was used to produce the modification. Per-region choices of compression algorithms can then be made responsive to the metadata without regard to the content of the image data itself.