[Pkg-gmagick-im-team] Bug#674718: imagemagick bug

[Vincent Fourmond]

  Hello,

On Sun, Jun 3, 2012 at 11:02 PM, Andrew Deason <adeason at dson.org> wrote:
>>   The thing is that, if I understand correctly, when you're using
>> -resize 217x159!, you resize the first layer to the desired size (ie
>> you multiply its size by a very large factor), but resize the other
>> ones to scale too (ie the second image, of size 217x159 gets scaled to
>> about the square of that). With -flatten, you flatten the selected
>> frames on the canvas, which happen to be the largest image (ie this
>> 217x159 squared). This is the expected behaviour.
>
> It is not expected for me that resizing the given image to 217x159
> yields a result larger than 217x159, since that is not how every single
> other image processing library I can find works (including, I believe,
> imagemagick version <= 5). This is not restricted to the 'convert'
> invocation given... I mean, for CloneImage (where the patch deals with),
> if I give 217 columns and 159 rows, I expect to get that back.
>
> That is, without flattening, resizing the given GIF to, say, half or
> double the canvas height/width with any other library generates an image
> approximately a quarter or quadruple the size. With the current version
> of imagemagick, you get huge results. (e.g., something like
> 'convert foo.gif -resize 108x79 bar.gif')

  No exactly. You get that:

foo.gif GIF 1x4 217x159+216+125 8-bit PseudoClass 2c 63B 0.000u 0:00.000
bar.gif[1] GIF 20x79 4340x3140+4320+2469 8-bit PseudoClass 32c 499B
0.000u 0:00.000

  You scaled the first frame to 20x79, and you scaled the canvas
accordingly. Why would you want that scaling apply only to part of the
image ? This wouldn't make any sense !

>> >> Are you trying to merge all the layer ? something like this :
>> >>
>> >> convert -resize '217x159!' -layers merge  'foo.gif[0]' foo.jpg
>> >
>> > The -layers option makes this incompatible with older ImageMagick
>> > releases, and GraphicsMagick, which is possibly why various software
>> > uses the other invocation.
>>
>>   Try this then:
>>
>> convert 'foo.gif[0]' -flatten -resize '217x159!'  foo.jpg
>>
>>   This does the resizing once all layers have been merged.
>
> I can't even verify that this does what you say (though I assume you are
> correct), since it takes too much memory to run on my machine.

  I'm surprised, as on mine this is instantaneous. Could you try with
the newer imagemagick from unstable, please ?

  Cheers,

      Vincent