[GEM-dev] YUV processing

Mathieu Bouchard matju at sympatico.ca
Thu Mar 25 09:25:37 CET 2004


On Wed, 24 Mar 2004, Mathieu Bouchard wrote:

> On Wed, 24 Mar 2004, B. Bogart wrote:
> 
> > I took a look at pix_compare and its close to what pix_mask did but
> > the issue is the threshold. With pix_mask you have 8 bits worth of
> > transparency data, where chroma-key and compare seem to only give you
> > two choices per pixel, image1 or image2. This makes things like video
> > noise really obvious and ugly. It would be great to have pix_mask
> > functionality in*some* form.
> 
> I don't understand: why can't you just multiply your image by the
> (greyscale) matte ?

woops, in case the problem is actually the creation of the matte: the
technique I use is that (essentially) I substract a desired colour, I
square it and sum, and then the result is the (square of the) distance
between the desired colour and the actual colour. Then I substract a
threshold, and apply something like tanh() to do a fuzzy comparison, and I
renormalise the -1..+1 range to 0..255 range. It gives me nice results.

________________________________________________________________
Mathieu Bouchard                       http://artengine.ca/matju





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