imagemagick_snippets.sh

# Flatten a transparent image with a white background:
convert -flatten img1.png img1-white.png

# Make an image transparent
convert -transparent '#FFFFFF' nontransparent.gif transparent.png

# convert an image into tiles
convert -size 3200x3200 tile:single_tile.png final.png

# making a montage from a collection of images
montage -geometry +0+0 -background transparent *png montage.png

# inverting colors
convert before.png -negate after.png

# generating a favicon
convert large_image.png -resize 16x16! favicon.ico
convert large_image.png -resize 32x32! favicon.ico

# generating a sprite (+/-)
convert *.png +append sprites.png
convert *.png -append sprites.png

ruby_imagemagick_snippet.rb

# adding numbers to a tiled image
cmd = (0..324).to_a.inject([]) do |cmd,n| 
  y=(n/25*32)+15; x=((n%25)*32)+15
  cmd << "-draw 'fill red text #{x},#{y} \"#{n}\"'"
end

`convert img.png #{cmd.join(' ')} annotated_img.png`