Describe the characteristics of image files (like resolution) with identify command that is part of ImageMagick and GraphicsMagick (gm identify) suite of tools.
Resizing with gm convert:
gm convert -size 300x400 -resize 300x400 +profile "*" <INPUT> <OUTPUT>
for file in *.jpg; do gm convert -size 150x200 -resize 150x200 +profile "*" ${file} small-${file}; done
Resizing with ffmpeg:
# width = 600, height calculate to retain aspect ratio
ffmpeg -i <INPUT> -vf scale=600:-1 <OUTPUT>
for file in *.jpg; do ffmpeg -i ${file} -vf scale=600:-1 small-${file}; done
# from flv to mp4
for file in *.flv; do ffmpeg -nostdin -hide_banner -loglevel error -i ${file} -vcodec libx265 -acodec copy ${file%.flv}.mp4; done
# from avi to mp4
for file in *.avi; do ffmpeg -nostdin -hide_banner -loglevel error -i ${file} -vcodec libx265 -acodec aac ${file%.avi}.mp4; done
# from mov to mp4
for file in *.mov; do ffmpeg -nostdin -hide_banner -loglevel error -i ${file} -vcodec copy -acodec copy ${file%.mov}.mp4; done
Source: imaging.md Created: 2025-01-05T20:28:33+02:00 Changed: 2025-07-05T19:38:48+03:00