Anyone ?
Assume you have many *.jpg files in a current folder. the thumnails will be generated under ./square, we are going to make square thumbnails for tons of jpg files in current directory
Crop & Resize without keeping aspect ratio, resize 400px , quality 75%mogrify -monitor -thumbnail x400 -resize 400 -gravity center -crop 400x400+0+0 +repage -format jpg -quality 75 -path square *.jpg
Crop & Resize to make thumbnails, keep respect ratio + Fill white BG to make same width and height , resize 400px , quality 75%mogrify -monitor -resize 80x80 -background white -gravity center -extent 80x80 -format jpg -quality 75 -path thumbs *.jpg
No fill BG, but keep aspect ratiomogrify -monitor -resize 80x80 -gravity center -format jpg -quality 75 -path thumbs *.jpg