Legacy ImageMagick Discussions Archive

Resizing images sometimes reduces colors to just one color. This depend on the input file and the size reduction.

Running:

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for f in $(seq 1 1000); do convert in.tif -verbose -resize x$f out.gif; done

produces output like this:

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[...]
in.tif=>out.gif TIFF 7027x5426=>263x203 263x203+0+0 8-bit Palette sRGB 116c 44KB 0.000u 0:00.000
in.tif=>out.gif TIFF 7027x5426=>264x204 264x204+0+0 8-bit Palette sRGB 115c 44.3KB 0.000u 0:00.000
in.tif=>out.gif TIFF 7027x5426=>265x205 265x205+0+0 8-bit Palette sRGB 1c 356B 0.000u 0:00.000
in.tif=>out.gif TIFF 7027x5426=>267x206 267x206+0+0 8-bit Palette sRGB 121c 45.3KB 0.000u 0:00.000
in.tif=>out.gif TIFF 7027x5426=>268x207 268x207+0+0 8-bit Palette sRGB 115c 45.3KB 0.000u 0:00.000
in.tif=>out.gif TIFF 7027x5426=>269x208 269x208+0+0 8-bit Palette sRGB 115c 46KB 0.000u 0:00.000
in.tif=>out.gif TIFF 7027x5426=>271x209 271x209+0+0 8-bit Palette sRGB 120c 46.5KB 0.000u 0:00.000
[...]

The problem started with version 6.9.0-2, 6.9.0-0 was still fine.

Tests on different machines and with convert or PerlMagick gave me different amount of problematic resize sizes. Most problems I had with PerlMagick and use of the CGI module on a FreeBSD 10.1 server (about 88 one color images for 1000 sizes). Less problems when not using the CGI module(???) (about 69) and still less when using convert or system(convert -resize ...) (about 2 images with one color only).

So for now I revert to system calls, but they aren't save as well.

Did anyone observe similar behaviour?

Thomas Mack

For someone to investigate, please provide an input file that shows the problem. You can put it somewhere like dropbox.com and paste the link here.

Oh yes.
I tested with http://th-mack.de/download/test/in.tif .

Problems on 6.9.0-2 / FreeBSD 10.1 e.g. on -resize x135 and x303 when using convert directly.

When using in PerlMagick, many more:

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#!/usr/bin/perl
use Image::Magick;

for(1..400) {
        my $image = Image::Magick->new;
        $image->Read("in.tif");
        $image->Resize(geometry=>"x$_");
        $image->Set(verbose=>'True');
        print $image->Write("out.gif");
        undef $image;
}

6.9.0-2 on Ubuntu: varying problems depending on the installation, it seems. I had an installation, where the problem appeared as minimum 9 colors on output, while neighbouring resize sizes used about 70 to 80 colors. Did a new installation of 6.0.9-2 and now have the '1c' output twice again.

We can reproduce the problem you posted and have a patch in ImageMagick 6.9.0-4 Beta, available by sometime tomorrow. Thanks.

Great - thank you!

Thomas Mack

Legacy ImageMagick Discussions Archive

convert -resize sometimes produces one-colored images

convert -resize sometimes produces one-colored images

Re: convert -resize sometimes produces one-colored images

Re: convert -resize sometimes produces one-colored images

Re: convert -resize sometimes produces one-colored images

Re: convert -resize sometimes produces one-colored images