How do I crop an animated gif using ImageMagick?

There's plenty of information about cropping images, but attempting to crop (or trim) animations produces strange results. Sometimes they flicker, or come with extra frames, or some frames crop correctly and others become offset. How do I prevent all this from happening?

convert input.gif -coalesce -repage 0x0 -crop WxH+X+Y +repage output.gif

• Animated gifs are often optimised to save space, but imagemagick doesn't seem to consider this when applying the crop command and treats each frame individually. -coalesce rebuilds the full frames.
• Other commands will take into consideration the offset information supplied in the original gif, so you need to force that to be reset with -repage 0x0.
• The crop itself is straightforward, with width, height, x offset and y offset supplied respectively. For example, a crop 40 wide and 30 high at an x offset of 50 = 40x30+50+0.
• Crop does not remove the canvas that it snipped from the image. Applying +repage after the crop will do this.

Even with the coalesce and repage, I could not get ImageMagick to crop and resize animated gifs very well.

I found a program called Gifsicle and it works great for manipulating animated gifs.

gifsicle --crop 0,0-100,100 --output out.gif in.gif

It can also do all sorts of other operations. Check it out!

Animations are often optimized, which means that some frames are smaller than others. So in ImageMagick you probably want to coalesce the animation before cropping.

convert in_animation.gif -coalesce -crop WxH+X+Y +repage -layers optimize out_animation.gif

You may need to add a -dispose method before reading the input animation to avoid a flicker. Also set the -delay and -loop at the end, if you want to make changes.

See

http://www.imagemagick.org/Usage/anim_basics/#dispose http://www.imagemagick.org/Usage/anim_basics/#coalesce http://www.imagemagick.org/script/command-line-options.php#layers