[GEM-dev] Re: meanwhile, in gempixutil...

[Georg Holzmann]

Hallo!

> the problem is (i believe), that YUV does not use the whole range from 
> 0..255 but something like 16..245 (or whatever: i didn't write it down 
> and now i cannot find it); i didn't add any clipping for this (which was 
> very stupid) because of performance reasons.
It fixed this for me some months ago, but didn't send it to the list 
(because I also changed the colors r and b because they were swapped with my
webcam ...)

e.g.: GemPixUtil.cpp, line 599:

  case GL_RGBA:
  case GL_BGRA_EXT:   //  <- this is the confusing: 
		      //   RGBA and BGRA is the same !!!
    {

	...
	  
	  // 1st row - 1st pixel
	  y=*py1++;
	  yy=y<<8;
	  //*pixels1++ = (yy + ub     ) >> 8; // r
	  *pixels1++ = CLAMP( (yy +      vr) >> 8 ); // r
	  *pixels1++ = CLAMP( (yy - ug - vg) >> 8 ); // g
	  //*pixels1++ = (yy +      vr) >> 8; // b
	  *pixels1++ = CLAMP( (yy + ub     ) >> 8 ); // b
	  *pixels1++ = 255; // a
	
	...

    }

so i think you only have to CLAMP the values (at least for me it worked much
better this way)

LG
Georg

> 
> oh, bless the lazy, but i really have to find the docs somewhere.
> 
> mfg.asd.r
> IOhannes
> 
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