One could start from the most comprehensive model , which is probably that closest to the physical phenomenon of electromagnetic radiation The physical/neurological phenomenon of perceived colour is very complicated. It involves a range of electromagnetic radiation and the way the retina cells are stimulated by it, and it is not really useful in computer graphics. For example, the colour orange may be perceived either by stimulation by the orange frequency (wavelengths from 590 to 620 nanometers), or it may be stimulation by two or more distinct frequencies ranging from the green to the red area. In real life, it will usually be a continuous spectrum, distributed in such a way that
and why there are various representations. That could certainly be interesting, but it might also be too much
For instance the primary colours are red, yellow and blue. No, they're not. It's what people learn when they grow up, but it's really wrong. The primary colours of the additive model are red, green and blue. With
Andy Little wrote: the red receivers are stimulated more than the green receivers. In fact, the exact way by which the human eye perceives colour is not yet definitely known. theory for the library. I think the presence or absence of such background documentation should not affect the decision whether to accept or reject GIL. three light sources in these colours, you can mix nearly every other colour a human can perceive. Because the human eye responds to these three colours the strongest, they most closely resemble the real model. Mixing these three colours results in white, while the absence of them is black. The primary colours of the subtractive model are magenta, cyan and yellow. Absence of these is white, presence of all three is white. They are used in printing, because the base of printing is a white ground, and because printed colour dots don't emit light, unlike CRT/LCD pixels.
Floating point RGB colours often have a range of intensities per color between 0 and 1, yet if I look at the sun I can burn my eyes. IOW what do those numbers actually represent in terms of the physical phenomenon of light.
Ah, that's an interesting question. In terms of the physical phenomenon, the answer is, "not much". The answer is found in engineering: 0 means nothing, while 1 means the brightest light the output device is capable of emitting (under its current brightness configuration).
IOW surely the goal is to try to model the physical phenomenon in the best possible way given a set of constraints imposed by hardware and software.
What do you mean now, the goal of the library or the goal of computer engineering? In terms of computer engineering, well, they actually achieved the physical model ;) In terms of the library, I disagree. The library should model not the physical concept of colour, because that is tricky to define, hard to understand, and complicated to work with. A library doing that might be nice for exact scientific simulation, but useless in every other discipline concerned with colour. Rather, the library should most closely model colour as it is used in computing, i.e. be capable of representing the various colour models in use (RGB, CMYK, HSV, ...) and providing access to all these, while allowing transparent use in cases where I don't care about them, allowing conversion between the various models, etc. It should be noted that GIL, at the moment, provides no proper concept of colour at all! It only provides the concept of a colour space, which is very close but not the same. The colour space defines the way in which pixels express their colour. But GIL does not have the concept of a colour independent of a pixel. In other words, it provides no way to express, for example, that the user has now chosen red as the colour of his drawing tool. Sure, you can make this very easily: either just misuse a single pixel for it (physical representation of the two is the same) or create a small class effectively copying it. Still, it might be called a mistake in the concept foundation of the library that the independent concept of Colour is missing. Sebastian Redl