You want to feather your image to look like the one on the right, but instead
you ended up with an image like the one on the left. What happened?
You probably placed your feathered image on top of a red (or green, or blue)
background thinking that you were later going to mark red as transparent.
When you told your transparency program to make red transparent, though,
it only marked one shade of red (i.e. 255,0,0 or
Feathering works by interpolating between foreground and background,
so there are several shades of red present that are not exactly
0xff0000 (that can't all be marked as transparent).
See the section on feathering in the
The effect is subtle, but if you look at the image on the left, you'll notice
a slight halo effect around the swirly shape. If you look closely, you'll
see that some of the pixels on the border between the swirl (which is
100% black) and the (simulated) page background (which is 25% black) are of
shades that are not between 25 and 100% black.
This is because the postscript swirl shape was rasterized on a white
background, so pixels padding the foreground and background are anywhere
between 0% black and 100% black.
Last modified: Thu Jun 20 16:07:38 1996