How to know the exact colour after a level of transparency being applied?

Hi,

I am filling an area with a specific colour, say [255 0 0 ], but with a level of transparency, say 0.5. So the actually colour that is going to fill the area is a lot weaker than a pure red 255 0 0.

If I use 'fill' to fill the area, then I

set(h, 'FaceAlpha', 0.5)

what colour do I get?

Is there anywhere I can find out this colour that actually being used to fill the area after 0.5 level of transparency being applied?

Answer 1

[Jan]

The color you see through a semitransparent element depends on the background. The rule is simple:

alpha      = rand;        % Anything between 0 and 1
Background = rand(1, 3);  % RGB
Foreground = rand(1, 3);
Visible    = Foreground * alpha + Background * (1 - alpha);  % resulting RGB color

[Salad Box]

That is really useful to know. Thank you so much!!

[Salad Box]

I am just wondering whether alpha can only be applied to RGB values? Can alpha be applied directly to Yxy values ?

[Jan]

I don't know. I even do not know the Yxy color space.

[Salad Box]

Brilliant. Thank you for your answers!! Very much appreciated!!