ffmpeg-recipes.sh

#find all videos in a folder and reduce their dimensions and or quality
#-crf lower is higher bitrate (better quality)
# -b 1000000 can be added, where you divide 1 GB by the video length in seconds (e.g. this is a 16m:40s video)
find . -type f -name "*.mp4" -exec bash -c 'FILE="$1"; ffmpeg -i "${FILE}" -crf 20 -s 1280x720 -acodec copy -y "${FILE%.mp4}.shrink.mp4";' _ '{}' \;

#optimize an mp4
ffmpeg -i input.mp4 -vcodec h264 output.mp4

#imagemagick:

#resize and change quality of a folder of images
magick mogrify -strip -quality 80% -resize 50% *.jpg

#specify max image dimensions:
magick mogrify -resize 1280x720 *.jpg

#resize with aspect ratio
convert input.png -geometry x600 output.png

#convert format from png to jpg
mogrify -format jpg *.png