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Typing convert on my system (14.04) produces:

The program 'convert' can be found in the following packages:
 * imagemagick
 * graphicsmagick-imagemagick-compat

Why are there 2 packages providing the same command?
How do I figure out which one should I use?

Follow-up

I used IM with command convert -layers Optimize output*.png output.gif and this produced a file of size 25903 bytes out of my 222 frames.

For the record the man page for IM convert says:

-layers method       optimize or compare image layers

For the sake of the test I uninstalled IM, installed GM and tried the supposedly equivalent command gm convert -delay 10 output*.gif animation.gif. It created an animated gif file with exactly the same size but different MD5sum.

Again, for the record the man page for GM convert does not mention option -layers.

This is not a bug in GM, it is just a different way of doing things. I guess I will be sticking with GM since it seems to be more actively maintained.

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According to the GraphicsMagick FAQ (which maybe outdated):

GraphicsMagick is originally based on (forked from) ImageMagick 5.5.2 in November 2002, from the version distributed by ImageMagick Studio LLC, which is itself forked in August 1999 from ImageMagick developed by E. I. du Pont de Nemours and Company starting in 1992. Other than utilities being executed as sub-commands of the 'gm' command, the command-line syntax and programming APIs remain entirely upward compatible with ImageMagick 5.5.2. A better question might be "How does ImageMagick differ from ImageMagick?" since ImageMagick continues to alter and evolve its interfaces so they are no longer completely compatible with earlier versions. While GraphicsMagick also adds new features, it does so in a way which assures that existing features work as they did before. ImageMagick focuses on adding new functionality and features and has dramatically mutated several times since the fork.

GraphicsMagick maintains a stable release branch, maintains a detailed ChangeLog, and maintains a stable source repository with complete version history so that changes are controlled, and changes between releases are accurately described. GraphicsMagick provides continued support for a release branch. ImageMagick does not offer any of these things.

Since GraphicsMagick is more stable, more time has been spent optimizing and debugging its code.

According to this SO question (also possibly outdated), GM is faster than IM. This blog post from 2013 concurs.

I have usually always used IM, and as the accepted answer in the above question indicates, for occasional low usage, it's fine.

Short answer: pick GM unless someone above you in authority specifically asks for IM. I'll be switching to it in short order.

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  • Great answer, thanks. I installed GM but it didn't work for me. It didn't support option -layers (I was trying to create a compressed animated .gif). Uninstalled it, installed IM and it worked fine.
    – sмurf
    Jul 7, 2014 at 1:04
  • @sмurf, ah. Then it is bug, since GM attempts to be compatible with IM. Could you post a bug report? graphicsmagick.org/… looks at animated GIFs, do the steps not apply?
    – muru
    Jul 7, 2014 at 1:17

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