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To composite an image of a cockatoo with a perch, use:
 
    gm composite cockatoo.miff perch.ras composite.miff
To compute the difference between images in a series, use:
 
    gm composite -compose difference series.2 series.1 difference.miff
To composite an image of a cockatoo with a perch starting at location (100,150),
use:
 
    gm composite -geometry +100+150 cockatoo.miff perch.ras composite.miff
To tile a logo across your image of a cockatoo, use
 
    gm convert +shade 30x60 cockatoo.miff mask.miff
    gm composite -compose bumpmap -tile logo.png
              cockatoo.miff mask.miff composite.miff
To composite a red, green, and blue color plane into a single composite image,
try
 
    gm composite -compose CopyGreen green.png red.png red-green.png
    gm composite -compose CopyBlue blue.png red-green.png composite.png
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