On Thu, 10 May 2007, Roman Haefeli wrote:
On Wed, 2007-05-09 at 14:55 -0400, Mathieu Bouchard wrote:
hm... if U=B-Y and V=R-Y, and if U and V are swapped by gem, does that mean, i can correct it by swapping B and R afterwards?
It would be the case if U,V was really exactly B-Y and R-Y respectively, but they also have special multipliers. Because, of this, the colormatrix you need would contain 9 non-zero values in it, which would be various fractions, not just ones. You could try a patch like:
[#color] | [#rgb_to_yuv] | [#inner (3 3 # 1 0 0 0 0 1 0 1 0)] | [#yuv_to_rgb] | [#reverse] | [#color]
This can show you the kind of correction that you'll need. Actually if you feed "3 3 # 1 0 0 0" instead of [#color] and replace the other [#color] by [#print] or [display], you'll get the matrix that you'll have to use the inverse of in [pix_colormatrix]. To find the inverse, you may use GF's [lti.MatrixInversion] or the equivalent from any other library (Johannes wrote at least one matrix invertor)
_ _ __ ___ _____ ________ _____________ _____________________ ... | Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada