Imagemagick

magick                    # used for resize, blur, crop, flip etc replaced magick when it dep
  -resize                 # resize image
  -strip                  # strip all metadata from image

identify                  # get stats on image
  -list format            # list formats available
  -verbose                # get even more info

mogrify                   # same as magick but write over original image

composite                 # overlaps one image over another

montage                   # images are tiled with option of border, frame, etc

compare                   # mathmatically and visually compare diff of images

stream                    # line by line print for large images

display                   # display image or sequence on any X server

import                    # saves any visible window on an X server.  Capture various screenshots

conjure                   # interprete and execute scripts written in Magick Scripting Language (MSL)

# convert all images in a directory
magick *.jpeg *.png

# resize image
magick image.jpg -resize 1024x768\! output_file.jpg

# reduce quality
magick image.jpg -quality 75 output_file.jpg

# create the pngs to be placed in the .ico
magick favicon.svg -resize 16x16 -strip favicon-16x16.png
magick favicon.svg -resize 32x32 -strip favicon-32x32.png
magick favicon.svg -resize 48x48 -strip favicon-48x48.png
magick favicon.svg -resize 64x64 -strip favicon-64x64.png

# place the pngs into the .ico file
magick favicon-16x16.png favicon-32x32.png favicon-48x48.png favicon-64x64.png favicon.ico

# check that the sizes are in the .ico
identify favicon.ico