Re: [pygame] "Making Games with Python & Pygame" free book

[Greg Ewing <greg.ewing@xxxxxxxxxxxxxxxx>]

Ian Mallett wrote:

> There is a "color space" that defines all possible colors.  "Primary 
> colors" are the colors we choose as basis vectors.  Both red-blue-yellow 
> and cyan-magenta-yellow are valid basis vectors;

I don't see how pure red, blue and yellow can be a valid subtractive
basis. Pure yellow pigment absorbs all blue light, and pure blue
pigment reflects only blue light. So yellow = -blue, and two of
your basis vectors are not linearly independent.

As far as I can see, red-blue-yellow only works to the extent that
your blue is cyan-like, and it works better if your red is
magenta-like.

The best coverage of the colour space is obtained when the basis
vectors are 120 degrees apart around the colour wheel. RGB and CMY
are two such sets; RBY is not.

Furthermore, anything other than RGB or CMY can't really be described
as additive or subtractive -- it's somewhere in between. RGB is the
only purely additive basis, and CMY is the only purely subtractive
basis. So if you're going to talk about *the* subtractive basis, then
it's CMY.

--
Greg