5th September 2002

Question: I was told that I want to use alfalfa blending on my graphics. This doesn't make any sense to me, is it true or is someone just pulling my leg?

Answer: Well, if someone was pulling my leg, I think I would just pry them off. Sorry, I couldn't resist a bad joke. I don't think it is really that someone is trying to "pull your leg" as much as a misunderstanding. What the person probably meant was ALPHA blending not alfalfa blending. To explain alpha blending you must first understand that each pixel has three channels of color information (red, green, and blue) but sometimes there is a fourth channel called the alpha channel. It is by using this alpha channel which controls the way that other graphics information is displayed, such as the level of transparency, that we can blend a background graphic and a foreground graphic. The best way I can explain alpha blending is to use the example that you are holding a photograph, if you hold a regular piece of glass over it then you can still see the picture. This is alpha blending with full transparency. If you hold a book over the photograph then you can only see the book. This is alpha blending with full opaqueness. You can find a happy medium holding a red smoked-glass over the photograph and your photograph now has a completely different look. You can still see all of the images in the photograph; it is just slightly blurred with a shade of red. Different programs refer to alpha blending differently (example: masks) so I will refer you to your applications help file for the proper way to administer and play with alpha blending on your image files.