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”
|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