A formula of color: how does MATLAB link indexed value of color with RGB format?

As known, MATLAB can plot graphics with colorbar and chosen colormap and also read/write images in RGB-scheme. And two color model are used, indexed (defined by double type C in range 0..1) and RGB.

How easy to define analytically function F:C->(R,G,B), i.e. r=r(c),g=g(c),b=b(c)?

With natural aasumptions: F(0)=(0,0,0),F(1)=(1,1,1) and F(?)=(1,0,0),.. F(?)=(0,1,1)

It would be helpful for intellectual colormaps....

Answer 1

[Jan]

As far as I know, you cannot map colors to a single parameter using an analytical function. The RGB colorspace uses 3 componnts, which cannot be projected onto a line.

The standard method is a lookup table using colormap.

Java can use a 24 bit value as a RGB color applying something like this

RGB = uint8(floor(rand(40, 20, 3) * 256));
Ind = RGB(:, 1) + 256 * RGB(:,2) + 65535 * RGB(:, 3);

Usually the alpha channel is added also and the colors are stored with 32 bits.

What do you want to achieve?

[Igor]

I think that simplest way to define this "like as" analytic function (thank you for code) is:

fist byte of C -- R-value

second -- G

third -- B

fourth (power) -- transparency

And the goal is achieved.

But it's interesting to imagine such function F as math formula.