mogrify

Perform operations on multiple images, such as resizing, cropping, flipping, and adding effects. Changes are applied directly to the original file. More information: https://imagemagick.org/script/mogrify.php.

• Resize all JPEG images in the directory to 50% of their initial size:
  mogrify -resize {{50%}} {{*.jpg}}
• Resize all images starting with "DSC" to 800x600:
  mogrify -resize {{800x600}} {{DSC*}}
• Convert all PNGs in the directory to JPEG:
  mogrify -format {{jpg}} {{*.png}}
• Halve the saturation of all image files in the current directory:
  mogrify -modulate {{100,50}} {{*}}
• Double the brightness of all image files in the current directory:
  mogrify -modulate {{200}} {{*}}