Projective alpha colour

P Willis

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
118 Downloads (Pure)

Abstract

Alpha colours were introduced for image compositing, using a pixel coverage model. Algebraically they resemble homogeneous coordinates, widely used in projective geometry calculations. We show why this is the case. This allows us to extend alpha beyond compositing, to all colour calculations regardless of whether pixels are involved and without the need for a coverage model. Our approach includes multi-channel spectral calculations and removes the need for 7 channel and 6 channel alpha colour operations. It provides a unified explanation of pre-multiplied and non pre-multiplied colours, including negative coordinates and infinite points in colour space. It permits filter and illumination operations. It unifies the three existing significant compositing models in a single framework. It achieves this with a physically-plausible energy basis.
Original languageEnglish
Pages (from-to)557-566
Number of pages10
JournalComputer Graphics Forum
Volume25
Issue number3
DOIs
Publication statusPublished - Dec 2006

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