iz: New fast lossless RGB photo compression

[cfeck]

Hi all, I finally managed to release a first preview of "iz" (ImageZero). Here some key stats:

• should be similar in speed as "arc a -mmm:3*8+1xb"
• compression rate similar to PNG for "good" photos
• BSD license

Caveats:

• only designed for 24 bit RGB natural photos
• compression of artificial images or very noisy images is bad
• no grayscale mode
• currently writes in machine-depended byte order, so files are not portable (they lack a header for now, anyway)

Some technical details:

• 3-pixel predictor
• single context value
• static Huffman tables (1 ... 6 bits per RGB pixel to encode context delta)
• branchless design (there is only one branch for the per-pixel loop, and one branch in the bitcoder to flush bitcache to memory)

More information:

• some compression results: http://skulpture.maxiom.de/playground/list-iz.txt
• as for timing results, try yourself, if you manage to build it
• source code at: https://github.com/cfeck/imagezero

I am very interested in any kind of feedback, since I am new to this forum. Thanks, Christoph