Alpha Blending
Alpha blending is the process of combining a translucent foreground color with a background color, thereby producing a new blended color. The degree of the foreground color's translucency may range from completely transparent to completely opaque. If the foreground color is completely transparent, the blended color will be the background color. Conversely, if it is completely opaque, the blended color will be the foreground color. Of course, the translucency can range between these extremes, in which case the blended color is computed as a weighted average of the foreground and background colors.
Alpha blending is a convex combination of two colors allowing for transparency effects in computer graphics. The value of alpha
in the color code ranges from 0.0 to 1.0, where 0.0 represents a fully transparent color, and 1.0 represents a fully opaque color. This alpha value also corresponds to the ratio of "SRC over DST" in Porter and Duff equations.
The value of the resulting color is given by:
If the destination background is opaque, then, and if you enter it to the upper equation:
The alpha component may be used to blend to red, green and blue components equally, as in 32-bit RGBA, or, alternatively, there may be three alpha values specified corresponding to each of the primary colors for spectral color filtering.
Note that the RGB color may be premultiplied, hence saving the additional multiplication before RGB in the equation above. This can be a considerable saving in processing time given that images are often made up of millions of pixels.
Read more about this topic: Alpha Compositing
Famous quotes containing the words alpha and/or blending:
“Imagination is a valuable asset in business and she has a sister, Understanding, who also serves. Together they make a splendid team and business problems dissolve and the impossible is accomplished by their ministrations.... Imagination concerning the worlds wants and the individuals needs should be the Alpha and Omega of self-education.”
—Alice Foote MacDougall (18671945)
“Exhaust them, wrestle with them, let them not go until their blessing be won, and, after a short season, the dismay will be overpast, the excess of influence withdrawn, and they will be no longer an alarming meteor, but one more brighter star shining serenely in your heaven, and blending its light with all your day.”
—Ralph Waldo Emerson (18031882)