[Magick-bugs] quantize introduces black areas (confirmation ofalready posted bug)

[Till Oliver Knoll]

Till Oliver Knoll schrieb:
> ...
> In other words: The 6.2.9 Q16 (Windows) is ALSO BUGGY (but at least 
> partially better than the 6.3.x).
> 
> I tried to reproduce this case with an artificial greyscale ramp image 
> with an alpha set to 254, but I could not yet reproduce this (the 
> greyscale ramp 256x256 image WORKS!).
> 
> I will try to upload my test images somewhere and let you know.

Here are some images to test with:

   alpha254.png:
   http://img442.imageshack.us/img442/6274/alpha254yy8.png
   An artificial colour ramp with alpha set all to 254

   alpha_grey254.png:
   http://img405.imageshack.us/img405/8581/alphagrey254ii1.png
   An artificial greyscale ramp with alpha set all to 254

   gradient_blue_none.png
   http://img265.imageshack.us/img265/9241/gradientbluenoneuo4.png
   As produced with ImageMagick 6.3.5:
   convert.exe -size 256x256 gradient:blue-none gradient_blue_none.png

   moto254.png
   http://img337.imageshack.us/img337/8986/moto254qx6.png
   A greyscale portrait with alpha all set to 254


The images where always converted with:

   convert.exe -colors 16 [in.png] [out.png]

I used 6.2.9 and 6.3.5, both compiled with quantum depth 16 and default 
settings. In the Visual configure application I unchecked the "Use X11 
stubs" though, but that should not have an influence, as I understand.

The resulting images from the 6.2.9:

   out_alpha254_6.2.9.png
   http://img508.imageshack.us/img508/1073/outalpha254629ef7.png
   GOOD

   out_alpha_grey254_6.2.9.png
   http://img523.imageshack.us/img523/6070/outalphagrey254629bt8.png
   GOOD

   out_gradient_blue_none_6.2.9.png
   http://img265.imageshack.us/img265/980/outgradientbluenone629gt7.png
   Surprisingly this is ALSO BAD

   out_moto254_6.2.9.png
   http://img508.imageshack.us/img508/2244/outmoto254629nh2.png
   BAD - as described in my previous post


The resulting images from the 6.3.5 (all bad):

   out_alpha254_6.3.5.png
   http://img510.imageshack.us/img510/4642/outalpha254635hj1.png
   BAD

   out_alpha_grey254_6.3.5.png
   http://img405.imageshack.us/img405/7584/outalphagrey254635oe9.png
   BAD

   out_gradient_blue_none_6.3.5.png
   http://img337.imageshack.us/img337/5844/outgradientbluenone635ro4.png
   BAD

   out_moto254_6.3.5.png
   http://img510.imageshack.us/img510/5971/outmoto254635ma2.png
   BAD


I ran the test images through a stock ImageMagick 6.0.7 as shipped with:

   %> uname -a
Linux enterprise 2.6.8-24.19-default #1 Tue Nov 29 14:32:45 UTC 2005 
i686 i686 i386 GNU/Linux

   %> convert -version
Version: ImageMagick 6.0.7 01/21/05 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2004 ImageMagick Studio LLC

Again quantization was done with convert -colors 16 [in.png] [out.png]

All resulting images look GOOD:

   out_alpha254_6.0.7.png
   http://img440.imageshack.us/img440/6239/outalpha254607vd6.png

   out_alpha_grey254_6.0.7.png
   http://img443.imageshack.us/img443/9337/outalphagrey254607ui7.png

   out_gradient_blue_none_6.0.7.png
   http://img263.imageshack.us/img263/7462/outgradientbluenone607pm3.png

   out_moto254_6.0.7.png
   http://img264.imageshack.us/img264/9523/outmoto254607mz6.png



Cheers, Oliver