GraphicsMagick Tutorial
GraphicsMagick is a fork of ImageMagick, aroud 2003.
GraphicsMagick home page http://www.graphicsmagick.org/
On Microsoft Windows, the command name for GraphicsMagick is gm.exe, For example gm.exe convert f1.png f2.jpg
If you are using GraphicsMagick, just add gm or
gm.exe in front of the command.