Images can be rendered to RLE and PBMPlus files. They can also be held in pixmaps and displayed using the a Tk photo image. Collectively they are referred to as image store. Image store is referenced by handles in various commands. Two attributes affect operations done on image storage, if they can be read, written or both and their scanning direction (top to botton, botton to top, or random).
Scanning direction determines if image store is accessed from top to bottom scan line, from bottom to top or randomly. File objects can only be accessed in one direction.
The following are the supported image store types and their attributes: