[theora-dev] yuv - rgb conversion without contrast decrease.

Lino Mastrodomenico l.mastrodomenico at gmail.com
Tue Nov 20 13:26:33 PST 2007

2007/11/20, Ribamar Santarosa de Sousa <ribamar.santarosa at gmail.com>:
> When I convert an yuv pixel into rgb using the recipies in
> http://www.fourcc.org/fccyvrgb.php I get an accurate color conversion
> but the contrast seems to be decreased.

I'm not sure, but maybe this is related to the fact that there are two
similar but incompatible YUV formats: the first is used mostly for
JPEG images and uses the full 0-255 range for each component, while
the second one (commonly used for video, including Theora) has smaller
valid ranges (16-235 for Y and 16-240 for U and V).

Slightly increased or decreased contrast is often a symptom of passing
an image in one of the two formats to a library that expect the other
one, without proper conversion.

Lino Mastrodomenico
E-mail: l.mastrodomenico at gmail.com

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