convert *.jpg -resize 1600 -quality 70% -depth 72 -units pixelsperinch resized.jpg

convert *.jpg -resize "460x460^" -gravity center -crop 460x460+0+0 +repage crop.jpg

montage crop*.jpg -geometry 460x460+0+0 mosaic.jpg

convert *.png -append -scale 50% stacked.png

convert -delay 5 -loop 0 *.png ../animation.gif

thanks to http://blog.room208.org/post/48793543478

ffmpeg -i video.mov -r 10 -s 640x400 -f image2 frames/frame-%03d.png

• -i video.mov the video file
• -r 10 the rate
• -s 640x400 the output size
• -f image2 the output format, a series of still images
• frames/frame-%03d.png is a printf format string specifying the output filenames, in this case dir/name-###.png, a series of PNG images called 001.png, 002.png, 003.png, and so on.

convert frames/*.png -delay 1x8 -coalesce -layers OptimizeTransparency animation.gif

• frames/*.png input files
• -delay 1x8 says that the animation should play a frame every 1/8 of a second. I computed this number by looking at the frame rate of the original video (24) and dividing by the number of frames each drawing plays for (3). Note that most browsers slow down animations that play faster than 20 frames per second, or 1/50 second per frame. Most videos play back at between 25 and 30 fps, so you may have to drop every other frame or so if you care about accuracy of playback speed.
• -coalesce apparently “fully define[s] the look of each frame of an [sic] GIF animation sequence, to form a ‘film strip’ animation,” according to the documentation.
• -layers OptimizeTransparency tells ImageMagick to replace portions of each frame that are identical to the corresponding parts of the preceding frame with transparency, saving on file size.
• animation.gif output file

convert ani.gif -coalesce ani.png
ffmpeg -f image2 -i ani-%d.png ani.mpg -vb 20M