Create thumbnail with fixed size and keep aspect ratio.
I would like to have fixed size for my thumbnails ex. 75×75 but the aspect ratio of it isn’t 1:1. To do this image must be centered, cropped and then resized. This could be done by bellow command:
mogrify -format jpg -resize "75x75^" -gravity center -crop 75x75+0+0 +repage 001.jpg
ps. mogrify is a part of ImageMagick