" To achive the effect first install Gimp. Gimp is a
crossplatform image editor available for Linux/Windows/Mac and
other Unix like systems. Download Gimp from GIMP - The GNU Image
"Post installation, open the source image in Gimp. Notice the
layer box at the right hand side.
" Duplicate the background layer by Right Click -> Duplicate
Rename the layer to Mask Layer by Right Click -> Edit Layer