Recently I needed to take two different animations and join them together to create a video using ffmpeg the result is here.

I needed to take an image with a size of 1920x1080 and crop it on the top and bottom to 1920x540. The simplest way to do this is to use convert from ImageMagick.

For a single image this looked like:

convert input.png -gravity Center -crop 1920x540+0+0 +repage output.png


By specifying the output size after cropping and to keep the image centered, convert automatically removed the top and bottom equally.

In batch the simplest way is to write a for loop or use mogrify

# crop all files in a folder (NOTE! that this is ALL files and not just images, convert might get confused)
for file in ../folder/*; do convert $file -gravity Center -crop 1920x540+0+0 +repage top_basename$file; done
# or if you want to crop a specific set of images
for i in $(seq 0 100); do convert input_$i.png -gravity Center -crop 1920x540+0+0 +repage output_$i.png; done  Finally we can join the two images together using the append command, note that -append will do a vertical append, and +append will do a horizontal append for i in$(seq 0 100); do convert top_$i.png bottom_$i.png -append final_\$i.png; done