find . -maxdepth 1 -iname '*jpg' -exec convert {} -thumbnail x200 -resize '200x<' -resize 50% -gravity center -crop 100x100+0+0 +repage -format jpg -quality 91 thumb/{} \;

find . -maxdepth 1 -iname '*jpg' -exec convert -define jpeg:size=200x200 {} -thumbnail 100x100^ -gravity center -extent 100x100 thumb/{} \;

http://www.imagemagick.org/Usage/thumbnails/#fit

Input: .jpg images of current directory\r\n\r\nOutput: the thumbnails will be generated in \'thumb\' folder

Generate Thumbnails with all same resolution (Cropped)

resize, image

Bash