Use ffmpeg to resize image

You can try this:

ffmpeg -i input.jpg -vf scale=320:240 output_320x240.png

I got this from source

Note: The scale filter can also automatically calculate a dimension while preserving the aspect ratio: scale=320:-1, or scale=-1:240


If you want to retain aspect ratio you can do -

./ffmpeg -i 1.jpg -vf scale="360:-1" 2.jpg

or if you want to resize based on input width and height, let's say half of input width and height you can do -

./ffmpeg -i 1.jpg -vf scale="iw/1:ih/2" 2.jpg

where

iw: input width
ih: input height