[Dogway]

I released RC9, this is a good candidate for 1.0 final so some feedback would be good, specially on argument coherency and chroma placement accuracy.
Recently added chroma placement option from/to RGB, linear_in/out options, and format out conversion.

The goal here is not speed as I can't compete with highly accelerated plugins but accuracy and reliance. The script is very straight forward, easy to use and easy to understand so it can be easily debugged. Also I want to make it a reference for accuracy, where all others compare against, for that I derived all the constants I could (except for RGB<->XYZ transforms), namely chroma placement shifts, kr, kb, kg coefficients, Pb, Pr, Nb and Nr coefficients, offset values for piecewise gamma function, etc.

Originally Posted by StvG

Shouldn't ColorSpace("601","709","spline36","spline36",true,false) be the same as YCbCrToRGB(YCbCrToRGB_mat("601")).RGBToYCbCr(RGBToYCbCr_mat("709")) ?

Now back to the hot topic, is RGB a color space? as I said, I don't think so. I call RGB a color format, although in fact it is a color "model", just like YUV. This is independent from color spaces, if you think about it all color space conversions happen through RGB (and XYZ) space, if you work with Nuke, Resolve, Photoshop, Blender... they are RGB based and color management aware at the same time.

Following some quotes I found while researching for a side project.

tftcentral:

Nearly every capture - or display device nowadays uses an RGB color model to describe the color for every pixel. (...). This data has a little meaning though without a color space assigned to it. A pixel with 8-bit color depth per channel with RGB value [255; 0; 0] would obviously be red. But without a color space assigned there would be no way to tell what the chromaticity for red should be.

Wikipedia: RGB:

The RGB color model itself does not define what is meant by red, green, and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green, and blue primaries are defined, the color model then becomes an absolute color space, such as sRGB or Adobe RGB; see RGB color space for more details.