From Sun, 13 Jan 2008 20:16:20 +0100 Pablo d'Angelo <[EMAIL PROTECTED]> wrote:
> > I've finished the draft UI and now I'm implementing a system where > > arbitrary filters can be inserted into the de-bayering chain. I'd > > say, 50% complete. > Sounds good. So we can correct TCA before debayering in the future? I'm not sure, I was going to insert all correction filters after de-bayer. The reason is that de-bayering algorithms all rely on fixed positions of the R/G/B pixels, and shifting them, especially with non-integer amounts, will break them completely. I'm a little unclean here, I'll try to explain a little more. Suppose you have some bayer image: R11 G21 R31 G41 G12 B22 G32 B42 One possible approach for doing TCA correction is this: suppose we should move R11 value from (0,0) to (0.5,0.3). The de-bayering algorithm cannot work with such things, it always relies on the fixed R-G-G-B matrix. It is (roughly speaking) something like (absolutely random formula, but gives the idea): G11 = (R11+B22)/4+(G21+G12)/2.66 B11 = ... Or, if put other way around, at, say, position B22 (1,1) you need to put the blue value from, say, (1.4, 0.6). How I can interpolate it? This will need some top-class debayering algorithm that can operate with arbitrary fractional coordinates, and I never heard of any such. However, this approach seems to me more appropiate for real implementation than the former. Perhaps one day in the future I will come with my own debayer algorithm which can compute any color component at arbitrary coordinates, but so far I'll just implement TCA correction post-debayer using the second approach. -- Andrew
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