gif from png sequence for twitter

twitter_gif_loop.sh

# Let's say an animation has frames {1,2,3,4}.png and is 24fps.
# To make it loop nicely on twitter, we want something like:
#
# 1 1 2 2 3 3 4
#
# at 48fps. The below command, using a bunch of hacks, will
# take a PNG sequence and create a gif with the above sequence.

# Note that 2.0833333... is 1/48, e.g., 48fps.

convert -limit thread 1 -delay 2.0833333333 $(echo *.png *.png | sed 's/ /\n/g' | sort | head -n  $(( $(ls -l *.png *.png | wc -l) - 1 )) ) out.gif