resize animated gif

[cssEXp]

here in this site, they do claim to be using imagemagick, and the gif resize is good, and filesize is less than original and quality exactly same, how are they doing it? try the manual resize on their site.

[cssEXp]

never mind, i asked them and they said they're using combination of IM and gifsicle, gifsicle for resize. Regardless, any way to maintain exact quality and low file size on im resize of animated gifs?

[anthony]

Resizing Animations has problems. First with optimization, then with Transparency, and finally with Color Optimization. A good, general GIF resizer is almost imposible with out some human like intelegence. See Animation Modification, Resizing Animations
http://imagemagick.org/Usage/anim_mods/#resize

I tryied this on the animation (resize to .5 the original size) using the animation at http://imagemagick.org/Usage/images/bunny.gif and the result looks as if it resized the image using a -sample type function, which avoids color problems, but does not do a good job. (See Resize Artifacts for a summery of resize problems)


I also tried it with the bunny on grass animation that had been Transparency Optimized
http://imagemagick.org/Usage/anim_opt/b ... ttrans.gif
The result was also not very good (again sample resized)

From this I feel that the it uses IM for the coalescing the animation to remove any frame optimizations present. That is because gifsicle often has problems with some types of frame optimizations, but the gifsicle with its 'sample resize' method to resize the animation, is highly aliased (dotty).

Much better results can be obtained simply by removing any transparency from the animation, using the normal IM resize, and then re-optimizing the animation, however the image size may not be very small as you may get with a horible 'sample' resize.

In summary... To simplistic, producing the 'crap' animations I see in just about every GIF animation collection out on the net.