creates a shadow (transparent) version of the image
i use this script for colorizing an img with CSS/HTML
i.e. I display the shadow img (in the HTML) and change the bg color with CSS
if u use the original colors from the picture u should get almost the same picture
u can play with the black-point/white-point values for less/more gray...
though it doesn't change much...
it meant to be use with uni-color img, but works with any img.