zpaq grayscale compression (intro to zpaql)

[mo_]

Hi all

Longtime lurker, first time poster. I recently spent a number of days getting up to speed on zpaql and how to write a zpaq image compression config for grayscale images. I could not find any information online about how to actually get started writing a zpaql config for 2D image compression, so I wrote up an intro on my blog:

http://www.modejong.com/blog/post15_...ale/index.html

With this config lena512.pgm would compress down to 138 kB with minimal CPU usage (for a zpaq configuration).

cheers
Mo

[thometal]

Nice, would it only possible to include custom written cfg into zpaq and not only in zpaqd which doesnt support the deduplication...........

[Matt Mahoney]

Archives created with zpaqd can be decompressed with zpaq. zpaqd archives are streaming (no dedupe), but you can mix types by appending streaming to journaling and vice versa.

Also, keep in mind in the comparison that bmp_j4.cfg is compressing a color image, which is 3x larger. But it is a nice tutorial to writing ZPAQL custom code.