[PD-dev] Re: [PD-announce] pdp v0.7

[daniel heckenberg]

another useful page for YUV<->RGB is this Intel page which goes through MMX
optimization of such conversions.

http://cedar.intel.com/cgi-bin/ids.dll/content/content.jsp?cntKey=Legacy::irtm_AP548_9996&cntType=IDS_EDITORIAL

daniel

tigital writes:

> >  > btw, i have a color conversion problem
> >>  and as people spoke about YUV/RGB colormaps,
> >>  i may ask for an advice here :
> >>
> >>  i'm using color conversions from effectv, the formulas are :
> >>
> >>  /*
> >>   * conversion from YUV to RGB
> >>   *   r = 1.164*(y-16) + 1.596*(v-128);
> >>   *   g = 1.164*(y-16) - 0.813*(v-128) - 0.391*(u-128);
> >>   *   b = 1.164*(y-16)                 + 2.018*(u-128);
> >>   * conversion from RGB to YUV
> >>   *   y =  0.257*r + 0.504*g + 0.098*b + 16
> >>   *   u = -0.148*r - 0.291*g + 0.439*b + 128
> >>   *   v =  0.439*r - 0.368*g - 0.071*b + 128
> >>   */
> >>
> >
> >i use exactly the same formula for conversion from the rgb colour model from
> >v4l and i've noticed some differences too compared to directly capturing in
> >yuv.. maybe the standard is not that standard?
> >
> >this page mentions another formula, along side the one above. maybe you can
> >try that one?
> >
> >http://www.fourcc.org/fccyvrgb.htm
> >
> weird...
> 
> ...I use the following conversions for gamma-corrected RGB and YUV:
> 
> Y = 0.299R + 0.587G + 0.114B
> U = -0.147R - 0.289G + 0.436B
>    = 0.492 ( B - Y )
> V = 0.615R - 0.515G - 0.100B
>    = 0.877 ( R - Y )
> 
> R = Y + 1.140V
> G = Y - 0.395U - 0.581V
> B = Y + 2.032U
> 
> ...of course, it turns out that it all depends on what the original 
> RGB is in, and differs if it's 16-235 or 0-255 per channel, and 
> whether your going for YUV, YCbCr:HDTV (Y709) or YCbCr:SDTV 
> (Y601)...for the record, the effectv conversions are Y601 based, with 
> RGB channels of 0-255...
> 
> another good reference is:
> http://www.faqs.org/faqs/graphics/colorspace-faq/
> 
> l8r,