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

[Vincent Fourmond]

On Wed, May 30, 2012 at 4:18 AM, Andrew Deason <adeason at dson.org> wrote:
> On Tue, 29 May 2012 11:05:51 +0200
> Bastien ROUCARIES <roucaries.bastien at gmail.com> wrote:
>
>> Could you please describe what you are trying to achieve. Flatten
>> means some special stuff in the gif context.
>>
>> And do not use geometry but resize or thumbnail operator.
>
> I did not generate that command line invocation, so I can't really
> explain the justification for it. It comes from the thumbnailing code in
> Gallery, some imageboard software, and probably some other places. It
> does not seem uncommon, and works as expected (at least, how I expected
> it to work) in GraphicsMagick.
>
> I'm not sure I understand upstream's response, though... is he trying to
> say that it is expected that the provided example generates a jpg that
> is tens of thousands pixels wide and tall? Even though the -size and
> -geometry options specified a size of 217x159? Using -resize instead of
> -geometry doesn't seem to change this behavior, but '-layers merge'
> does.

  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.

>> 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.

  Cheers,

      Vincent