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

[Till Oliver Knoll]

Till Oliver Knoll wrote:
> Peter Pimley schrieb:
> 
>> ...
>> With the help of a few other posters, we found that earlier versions did
>> not show the problem.  It was only very recently introduced.  6.3.4
>> seems to be OK, whereas 6.3.5 is not.
> 
> 
> I just downloaded the latest 6.3.4 sources for Windows (which include 
> the "VisualMagick" subfolder), e.g. from here
> 
> 
> ftp://ftp.fu-berlin.de/unix/X11/graphics/ImageMagick/windows/ImageMagick-6.3.4-10.zip 
> 
> 
> and it shows the same buggy behaviour: "black areas" are also produced 
> with the following command:
> 
>    convert -size 256x256 gradient:blue-none -colors 16 out.png
> 
> Am going to try the previous version(s) ...

I have tried the version 6.3.2 which also shows the buggy "black area"! 
And apart from Windows (which does not work either) I have also 
downloaded the 6.3.2 sources and compiled on an older SuSE 8.2:

   %> ./configure
   %> make
   %> make install

(See configure output at the bottom, just in case)

The utilities got installed on /usr/local/bin etc.

The following produces the "black area" bug, also on Linux, version 6.3.2:

   %> uname -a
Linux cola 2.4.20-4GB #1 Mon Mar 17 17:54:44 UTC 2003 i686 unknown 
unknown GNU/Linux

   %> /usr/local/bin/convert -version
Version: ImageMagick 6.3.2 09/13/07 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2007 ImageMagick Studio LLC

   %> /usr/local/bin/convert -size 256x256 gradient:blue-none -colors 16 
out.png

This produces the black area, around in the middle of the image.

I understand that people have claimed that the 6.3.4 works, e.g. on Mac. 
  And I can imagine why: when one uses the ImageMagick 'display out.png' 
command the black area might be easy to miss (especially when it was 
produced with -colors 256, as suggested in the original bug report by 
Peter, because then the "black area" is very "thin"). This is because of 
the transparency and the greyish checker pattern in the background, so 
the black stripe is hardly noticeable.

But when you display the 'out.png' e.g in Konqueror (or with XnView on 
Windows, for example) which blends against a white background (instead 
of the grey checker pattern) then the black area becomes clearly visible.


The stock ImageMagick which ships with SuSE 8.2 is fine though:

   %> convert -version
Version: ImageMagick 6.0.6 08/25/04 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2004 ImageMagick Studio LLC

It seems that this version does not support the 'gradient:blue-none' 
argument (it produces an image all blue, probably because 'none' is not 
a recognized keyword?), but when converting an image with alpha all set 
to 254 for example it works fine (whereas 6.3.2-6.3.5 do not, as 
explained in a previous post).



Summary: ImageMagick 6.3.2 up to 6.3.5-8 (the latest stable version as 
of now) show the "black areas" when quantizing images with alpha values 
< 255.





Configure 6.3.2 (Linux SuSE 8.2) output, in case that matters:


ImageMagick is configured as follows. Please verify that this configuration
matches your expectations.

Host system type : i686-pc-linux-gnu

                   Option                        Value
-------------------------------------------------------------------------
Shared libraries  --enable-shared=yes           yes
Static libraries  --enable-static=yes           yes
Module support    --with-modules=yes            yes
GNU ld            --with-gnu-ld=yes             yes
Quantum depth     --with-quantum-depth=16       16

Delegate Configuration:
BZLIB             --with-bzlib=yes              yes
DJVU              --with-djvu=yes               no
DPS               --with-dps=yes                yes
FlashPIX          --with-fpx=no                 no
FontConfig        --with-fontconfig=yes         no
FreeType          --with-freetype=yes           yes
GhostPCL          None                          pcl6 (unknown)
Ghostscript       None                          gs (7.05.6)
Ghostscript fonts --with-gs-font-dir=default 
/usr/share/ghostscript/fonts/
Ghostscript lib   --with-gslib=yes              no
Graphviz          --with-gvc=yes                no
JBIG              --with-jbig=yes               no
JPEG v1           --with-jpeg=yes               yes
JPEG-2000         --with-jp2=yes                no
LCMS              --with-lcms=yes               yes
Magick++          --with-magick-plus-plus=yes   yes
PERL              --with-perl=yes               /usr/bin/perl
PNG               --with-png=yes                yes
RSVG              --with-rsvg=yes               no
TIFF              --with-tiff=yes               yes
Windows fonts     --with-windows-font-dir=      none
WMF               --with-wmf=yes                yes
X11               --with-x=                     yes
XML               --with-xml=yes                yes
ZLIB              --with-zlib=yes               yes

X11 Configuration:
   X_CFLAGS     = -I/usr/X11R6/include
   X_PRE_LIBS   = -lSM -lICE
   X_LIBS       = -L/usr/X11R6/lib
   X_EXTRA_LIBS =

Options used to compile and link:
   PREFIX      = /usr/local
   EXEC-PREFIX = /usr/local
   VERSION     = 6.3.2
   CC          = gcc
   CFLAGS      = -g -O2 -Wall -W -pthread
   CPPFLAGS    = -I/usr/local/include
   PCFLAGS     =
   DEFS        = -DHAVE_CONFIG_H
   LDFLAGS     = -L/usr/local/lib -L/usr/X11R6/lib -L/opt/gnome/lib 
-Wl,--rpath -Wl,/opt/gnome/lib -lfreetype -lz
   LIBS        = -lMagick -llcms -ltiff -lfreetype -ljpeg -lXext -lSM 
-lICE -lX11 -lXt -lbz2 -lz -lpthread -lm -lpthread
   CXX         = g++
   CXXFLAGS    = -g -O2 -Wall -W -pthread