Graphic PIZiadas

Graphic PIZiadas

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Alpha compositing: Porter-Duff rules

Porter Duff rulesBy forming synthesis or edit images use a series of mathematical operations “mixed” or “merge” colors ghosting.

The rules governing this composition are included under what is known as Porter-Duff rules after the first article documented that structured.

Known as “compositing” the process and operations for adding (compose) to a new given image ghosting.

Thomas Porter y Tom Duff, members “Computer Graphics Project” in the company Lucasfilm Ltd. published an article entitled “Compositing Digital Images” as set out in “Computer Graphics Volume 18, Number 3 July 1984” published by ACM, which has become a key reference when analyzing the process of “superposition” Picture.

While we have described 12 operations or rules for the superposition of two images, key may be restricted to eight; we turn differentiate between cases where images are fully opaque or have a “channel” transparency.

Schematically, the following are the basic operations:

The meaning is presented in the following table, in which the fund is called “destination” and the new image “source”

Name Description
SrcOver Place the pattern on the target source
DstOver Destination on source
Clear Deletes destination under the source
Src Overlay source destination without alpha channel on
SrcIn Ditto above but with alpha channel
DstIn Displays the destination that matches the source
SrcOut Part of the fountain outside the destination
DstOut Part of the source destination outside
  • Compositing Digital Images” “Computer Graphics Volume 18, Number 3 July 1984” published by ACM: © 1984 ACM 0-89791-138-5/84/007/0253
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Image Synthesis