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December 2009
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2009.12.12 18:19 "Re: YCbCr", by Bob Friesenhahn
On Sat, 12 Dec 2009, Gene Amtower wrote: > So, you can store either RGB, YCbCr, or CMYK data in TIFF files. > However, due to the variable conversion > algorithms used for converting to/from CMYK or YCbCr, anything other than > RGB is probably not likely to work > outside of whatever application creates them. Is that a correct > statement? While CMYK is quite variable since it is device dependent, YCbCr is defined by several ITU specifications (Rec.601 or Rec.709) and is therefore quite well defined. While YCbCr should work quite nicely in TIFF, the only common use seems to be in conjunction with JPEG compression. Except for issues related to subsampling (which requires horizontal, and sometimes even vertical filters), YCbCr is not difficult to work with. > It just seems to me that storing image data in anything other than > RGB-based formats is not a good idea for most general usages and > should only be employed if the images are used for internal program > processing only. Otherwise, the matrix employed to generate the > YCbCr or CMYK format is not known to a reader of the file. For general usage, you should stick to baseline TIFF. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/