[GEM-dev] [pix_video]: issue with swapped colors

[Roman Haefeli]

On Wed, 2007-05-09 at 14:55 -0400, Mathieu Bouchard wrote:
> On Wed, 9 May 2007, IOhannes m zmoelnig wrote:
> 
> > another way (less efficient, and wrong if matju is right):
> > videoV4L.cpp:173: add "m_image.image.swapRedBlue();"
> 
> In my last mail, I didn't claim that the problem was surely (U,V) 
> swapping, I said that it was a possibility, but now I think I should have 
> said that it's almost certainly that.
> 
> It's because, in the encoder of the camera, U and V are necessarily 
> encoded as properly scaled B-Y and R-Y anyway, because else it would be a 
> blatant bug, and I can't imagine a camera setting that would allow for 
> violating the definitions of U and V to make them confuse R and B. 
> (although... now that I think of it, I'd really enjoy a camera that allows 
> me to set the contrast separately on Y, U and V.)
> 
> Therefore, U and V come as correct through the cable and the driver and/or 
> the GEM object confuses them.
> 
> makes sense?

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? i tried to fix
the wrong colors by swapping R and B using [pix_colormatrix] and a list
[0 0 1 0 1 0 1 0 0( and the result looked very similar to the picture i
get now with the 'fixed' videoV4L.cpp. or in other words: does swapping
U and V in YUV-colorspace and swapping B and R in RGB-colorspace have
the same effect?

roman


		
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