An Imagic picture is a raster graphic in a format used by the Atari ST series in conjunction with animation. It can be compressed or not, and low, medium, or high-res. The file extension .ic1 is used for low-res, .ic2 for medium, and .ic3 for high. Compressed image data may also be "delta compressed", where it is stored as a set of differences from a reference image (in a separate file named within the headers of the current one). This is commonly used for animation frames.
Files start with the ASCII string
IMDC. The following word is 0, 1, or 2 for low, medium, and high-res respectively.