ge@dbf.kun.nl (Ge' Weijers) (03/04/91)
In a German-language photography journal I saw a (nontechical) explanation of the forthcoming Kodak Photo-CD. Are the specifications known yet? The article mentioned coding pixels in YCC coordinates in stead of YIQ or RGB. What is this? The article mentioned that YCC had its advantages when the picture was compressed by a lossless method. Ge' -- Ge' Weijers Internet/UUCP: ge@cs.kun.nl Faculty of Mathematics and Computer Science, (uunet.uu.net!cs.kun.nl!ge) University of Nijmegen, Toernooiveld 1 6525 ED Nijmegen, the Netherlands tel. +3180652483 (UTC-2)
allanh@netcom.COM (Allan N. Hessenflow) (03/06/91)
In article <2804@wn1.sci.kun.nl> ge@dbf.kun.nl (Ge' Weijers) writes: >In a German-language photography journal I saw a (nontechical) explanation >of the forthcoming Kodak Photo-CD. Are the specifications known yet? >The article mentioned coding pixels in YCC coordinates in stead of >YIQ or RGB. What is this? The article mentioned that YCC had its advantages >when the picture was compressed by a lossless method. It probably should have said YCbCr which is a colourspace defined in CCIR-601 (although I've recently been informed that there are other different colourspaces also called YCbCr); it's similar to YIQ in that luma and chroma are separate. I don't see any advantage to YCbCr in lossless systems; in fact the conversion from to RGB to YCbCr and back is normally lossy in itself. This is because YCbCr is a larger colourspace than RGB, so if the same number of bits are used to represent a colour then the transform from YCbCr to RGB can not produce all possible RGB values. YCbCr does have advantages for lossy compression because more information can be thrown away from the chroma channels than from luma. allan -- Allan N. Hessenflow {apple|claris}!netcom!allanh allanh@netcom.com