An 8-bit layer in a graphics file format that is used for expressing translucency. The additional eight bits per pixel serve as a mask and represent 256 translucency levels from entirely clear (0) to opaque (255), with levels in between representing the degree of haziness. See translucency, RGBA and HSLA.|
The TIFF and PNG graphics formats support the 8-bit alpha channel, whereas GIF89a supports a 1-bit channel that allows one color on the palette to be translucent (see GIF). Graphics formats native to their image editing application may support multiple alpha channels. For example, Photoshop's native PSD format can have a total of 24 channels, including color channels (RGB, CMYK, etc.) and alpha channels. When converted to another graphics format, the alpha channels are reduced to one or none depending on the destination format. See alpha blending.