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

[Till Oliver Knoll]

Till Oliver Knoll schrieb:
> Till Oliver Knoll schrieb:
>> Hello!
>> ...
>> http://studio.imagemagick.org/pipermail/magick-bugs/2007-August/002700.html 
>>
>> ...
>> First I could reproduce the behaviour as described in the 002700.html 
>> description above, see attachemenet 'problem.png':
>>
>>   convert -size 256x256 gradient:blue-none -colors 256 problem.png
>>
>> Another image 'test_in.png' reproduces this problem with an image of 
>> mine. Note again the blueish colours which are affected which could 
>> lead to the source of the bug.
>  > ...
> 
> Uh oh... seems like the attachements have been stripped by the mailing 
> list robot - at least I did not get them.
> 
> Let me know if I should send them in private to some email address.
> 
> Anyway, the bug is reproducible with the above command line.
> 
> I suspect that only the "Q8" versions are affected since all posts to 
> the above link said it works, but obviously they were using the "Q16" 
> version.
> 
> Right now I'm rebuilding from source with the "Q16" option enabled and 
> see if that makes a difference.

Hmmm, I must confirm that this bug also appears in the "Q16" version:

1. Download ImageMagick-6.3.5-8-Q16-windows-dll.exe
    from http://www.imagemagick.org/script/binary-releases.php#windows

2. Open a cmd.exe prompt

3. > convert -size 256x256 gradient:blue-none -colors 256 problem.png

A certain colour which should be blue is rendered black (dark) instead, 
as described here:

http://studio.imagemagick.org/pipermail/magick-bugs/2007-August/002700.html


Let me know if I should send you some sample images (96x96 pixels, PNG, 
as described in my first message) which also show this behaviour, but in 
a more drastic way.


Cheers, Oliver