Quicktime File Format (2012-08-14).pdf

Basic Data TypesRGB ColorsTable 5-3QuickTime graphics modesModeUsesopcolorCodeDescriptionCopy0x0Copy the source image over the destination.Dither copy0x40Dither the image (if needed), otherwise do a copy.Blendyes0x20Replaces destination pixel with a blend of the source anddestination pixel colors, with the proportion for eachchannel controlled by that channel in the opcolor.Transparentyes0x24Replaces the destination pixel with the source pixel if thesource pixel isn't equal to the opcolor.Straight alpha0x100Replaces the destination pixel with a blend of the sourceand destination pixels, with the proportion controlled bythe alpha channel.Premul whitealpha0x101Premultiplied with white means that the color componentsof each pixel have already been blended with a white pixel,based on their alpha channel value. Effectively, this meansthat the image has already been combined with a whitebackground. First, remove the white from each pixel andthen blend the image with the actual background pixels.Premul blackalpha0x102Premultiplied with black is the same as pre-multiplied withwhite, except the background color that the image hasbeen blended with is black instead of white.Straight alphablendyes0x104Similar to straight alpha, but the alpha value used for eachchannel is the combination of the alpha channel and thatchannel in the opcolor.Composition(dither copy)0x103(Tracks only) The track is drawn offscreen, and thencomposed onto the screen using dither copyRGB ColorsMany atoms in the QuickTime file format contain RGB color values. These are usually stored as three consecutiveunsigned 16-bit integers in the following order: red, green, blue.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.322