compression algorithm for bitmap images

Question

Are there algorithms for lossless compression of bitmap images that beat the LZ family? Suitable for an embedded environment.

Requirements:

• maximum compression
• geared towards images with low bpp: 2-8, max 15
• low memory consumption or in-place decompression
• fast decompression

Answer 1

One candidate might be Rad Game Tools' Smacker algorithm. Their free compression tools can be downloaded at http://www.radgametools.com/smkdown.htm

Advantages: Smacker video has been in use since the mid-1990's and can decode in real-time on i486 computers with meager amounts of RAM (by today's standards). Although it's a video format, many games have used it for still images.

Disadvantages: While it's paletted, I'm not entirely sure it's lossless. It probably has dials for that, though. Also, if you're planning to distribute a product based on it, you are expected to pay for a license. I have no idea what kind of platform you need this for, but they might not have a decoder ready for you. Fortunately, there's an open source decoder in the FFmpeg project but again, licensing issues-- don't know if they would sign off on you using the open source decoder even if you bought a license.

If this doesn't fit your needs, you'll have to supply more details with more concrete goals, starting with a bake-off demonstrating how the common compression formats operate on your corpus and what specific targets (compression and speed-wise) you would like to achieve.