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palm libpng port by Michal Seliga aka Selmi, selmi@centrum.sk
some help came from Donald C. Kirker who is also first person but me who is using it
some help came from Jeremy Bernstein

used libpng-1.2.18, zlib-1.2.3, peal-29.12.2004

details on www.sf.net/palmpng

WARNING
its extremely unfinished version which is released is such sorry state only becauseof its
increasing popularity (i give it to anyone who asks politely so there is no point to not
putit on page). but note:

 ITS UNFINISHED AND I TAKE NO RESPONSIBILITY FOR ANY DAMAGE IT WILL DO!!!


todo: 

convert all this to shared library
  - possibilities: 1)make own api 2)export all libpng and zlib functions
  - preferrably: export all libpng and zlib functions + keep myown helper api to decode image and painting it
  
can i get rid of peal? i don't know how.... 
(problem - i need callbacks for memptrnew at least, because i must use Glue library to allow more then 64kb in one block. for callback i need 2 global variables and in pure pnolet globals don't work)
  
can i get rid of zlib and use SysZLib? but builtin zlib should be faster anyway

if all this will work add support for writing  (creating pngs - is it needed?)
   
try to make m68k version? i didn't even tried that yet

i was just thinking maybe it would be nice to add possibility to dither images, basic converting of 32bpp image to 16bpp doesn't looks nice sometimes.

make it support other then 16bpp color mode (using lookup table for rgb->palette conversion? this would need dithering for sure)
  or forget about it, all modern devices know 16bpp modes

enhance png optimizer tool.
    - create backups
    - ability to work recursively
    - save 'optimized' file only when its smaller then original 
    - maybe try if file can be converted to 8bpp or even smaller (with palette) after optimizing, it should create even smaller files
    - check if alpha chanel is neccesary and remove itif its not needed


how it works:
all files which belong to any 3rd party library are in their directories in lib directory
these which i need are symlinked to main directory
these i need and i changed they are copied and changed: pngconf.h, zutil.h - only change is that they include palmpng.h and in zutil is also one #ifdef to new define PALMOS
i added new files: armtypes.h, macros.h, palmpng.c, palmpng.h
 armtypes.h has defines for types i am used to from palmos api
 macros.h has byteswapping macros
 palmpng.h has definitions from zlib a libpng to make it work
 palmpng.c has functions i needed to provide (malloc, free, abort), some for debugging (alert) and my test depackpng


alpha channel is converted from 0.255 as stored in pngfile to 0..31 reason for this is that i was using basic windows for transparency layer in my app and i wanted it to fit to 5:6:5 color scheme

test program:
makes slideshows of 6 pngs
 1) RGB
 2) 256 colors with palette
 3) RGB with alpha channel
 4) gray
 5) black&white
 6) gray with alpha channel