Re: Mistake on the colorspace page in the API doc

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Wouter,

On Sunday 26 May 2013 15:34:26 Wouter Thielen wrote:
> Hi all,
> 
> I have been trying to get the colors right in the images grabbed from my
> webcam, and I tried the color conversion code on
> http://linuxtv.org/downloads/v4l-dvb-apis/colorspaces.html.
> 
> It turned out to be very white, so I checked out the intermediate steps,
> and thought the part:
> 
> ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */
> EG = clamp (g * 255);
> EB = clamp (b * 255);
> 
> 
> should be without the * 255. I tried removing *255 and that worked.

Good catch. I would instead do

y1 = (Y1 - 16) / 219.0;
pb = (Cb - 128) / 224.0;
pr = (Cr - 128) / 224.0;

and keep the E[RGB] lines unmodified to keep lower-case variables in the [0.0 
1.0] or [-0.5 0.5] range.

Would you like to post a patch for the documentation ? If not I can take care 
of it.

-- 
Regards,

Laurent Pinchart