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

[Till Oliver Knoll]

Till Oliver Knoll schrieb:
> ...
> After digging the web for older ImageMagick sources I came up with the 
> 6.2.9-0, as downloaded from some (out of sync?) mirror:
> 
> 
> http://gsmp.tfh-berlin.de/mirror/t2-source/6.0/I/ImageMagick-6.2.9-0.tar.bz2 
> 
> 
> which apparently is the latest in the 6.2.x series.
> 
> I compiled it on SuSE 8.2 with the usual
> 
>   %> ./configure
>   %> make
>   %> make install
> 
> Seems like the gradient:blue-none (the 'none' keyword) was only 
> introduced in the 6.3.x series, so I could not test it with the
> 
>   convert -size 256x256 gradient:blue-none -colors 16 out.png
> 
> (which produces an all blue image without transparency)
> 
> but my test image 'alpha254.png' (some image with alpha channel set 
> uniformly to 254) which fails with the 6.3.x WORKS with this version 
> 6.2.9-0!
> 
> Seems like the bug was introduced somewhere in the 6.3.x.

Hmmm, that's interesting: I compiled this very same version 6.2.9-0 on 
Windows first with default settings and it WORKED as well.

Then I ran the Visual configure project again, edited the configure.h.in 
file and #defined the Quantum depth to be 8 (instead of 16):

   // magick-config.h.in
   #define QuantumDepth 8

And guess what, the "black area" bug APPEARED AGAIN!

So whereas I compiled on Linux the 6.3.x always with default settings 
(quantum depth 16) and it never worked, the 6.2.9 seems to work, but 
ONLY when quantum depth is set to 16! When setting the quantum depth to 
8 then the 6.2.9 ALSO FAILS (at least on Windows).

I have done this last test only on Windows, but I'd expect the same 
buggy behaviour on Linux with the 6.2.9, quantum depth 8.



Summary:

- 6.2.9 works with quantum depth 16 (Linux, Windows)
- 6.2.9 does NOT work with quantum depth 8 (Windows, did not try Linux)
- 6.3.x does NEVER seem to work (tried 6.3.4 and 6.3.5 on both Windows 

                                  and Linux, 6.3.2 only on Linux;
                                  Windows: tried with both Q8 and Q16;
                                  Linux: tried Q16 only (default))


Hope that helps in tracking down the bug.

Cheers, Oliver