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2010.06.14 14:57 "Re: Class Y images with alpha channels", by Bob Friesenhahn
On Mon, 14 Jun 2010, Thomas Richter wrote: > > *) Given I have an alpha channel, how is it interleaved with the > remaining channels? Is the alpha channel subsampled (I suppose not, but > I don't know). Is it > YYYYCbCrAAAA or is it YYYYAAAACbCr, or YYYYCbCrA? While it perhaps does not matter to TIFF, in the video world of YCbCr, the alpha channel is called the "key" channel and is normally provided via a separate image or signal input. It is surely exceedingly rare to associate alpha in YCbCr within the same image, although I think that SMPTE DPX can technically do so. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/