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

[Andrew Deason]

On Wed, 30 May 2012 09:33:17 +0200
Vincent Fourmond <fourmond at debian.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')

> >> 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 am going to be travelling for a little bit, so I may not be able to
respond to anything for the next week or two.

-- 
Andrew Deason
adeason at dson.org