The alpha channel is used to specify an alpha value for each color pixel. The alpha value is used to control the blending, on a pixel-by-pixel basis, of two images. Alpha typically has a normalized value of 0 to 1. In a computer environment, the alpha values can be stored in additional bit planes of frame-buffer memory. When you hear about 32-bit frame buffers, what this really means is that there are 24 bits of color, 8 each for red, green, and blue, along with an 8-bit alpha channel. Also see Alpha Mix.