[Cin] Some tests on blending

[Georgy Salnikov]

On Thu, 27 Mar 2025, Andrea paz via Cin wrote:

> workaround by IgorBeg. I have tried further testing, now that we have
> Blend Algebra that allows us to customize the various Blends.

Regarding Blend Algebra I'd point out to the following details.

In patchbay's overlay modi or in the Overlay plugin the results can differ
depending on the RGBA or YUVA color model. But in Blend Algebra, as long as
you have 'COLORSPACE_RGB' statement in the function code, and the other
default settings, comparing RGBA with YUVA is useless: both are converted by
the plugin's engine to RGBA-Float before calling user's expressions and
therefore should give identical results by definition.

If you really want to compare RGBA with YUVA under Blend Algebra, then you
have either to change COLORSPACE_RGB to COLORSPACE_YUV in the blend
function, or to remove the 'COLORSPACE' declaration completely, or to change
the colorspace parameter in the plugin dialog from the default 'by function'
to the explicit 'RGB' or 'YUV' value. Have you done this?

If your color model is YUV without alpha channel, then you cannot see the
result if it is not placed on Top: the upper track will hide it completely.

By the way, under Blend Algebra you have the possibility to calculate
overlay arithmetic also in the HSV color space ('COLORSPACE_HSV'), can
hardly imagine what should come out:)
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Georgy Salnikov
NMR Group
Novosibirsk Institute of Organic Chemistry
Lavrentjeva, 9, 630090 Novosibirsk, Russia
Phone   +7-383-3307864
Email   sge at nmr.nioch.nsc.ru
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