alpha channel

English

Etymology

Coined by Alvy Ray Smith and Ed Catmull in the 1970s. Smith writes: "We called it that because of the classic linear interpolation formula $\alpha A+(1-\alpha )B$ that uses the Greek letter $\alpha$ (alpha) to control the amount of interpolation between, in this case, two images A and B".[1] That is, when compositing image A atop image B, the value of $\alpha$ in the formula is A's alpha channel.

Noun

alpha channel (plural alpha channels)

(computer graphics) A numerical value specifying a level of translucency to be applied to a colour.

Translations

numeric value

Finnish: alfakanava
Portuguese: canal alfa m

References

Alvy Ray Smith (1995 August 15) “Alpha and the History of Digital Compositing”, in alvyray.com‎, archived from the original on 25 October 2021, page 6

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[1] Alvy Ray Smith (1995 August 15) “Alpha and the History of Digital Compositing”, in alvyray.com‎, archived from the original on 25 October 2021, page 6