How can I implement colors in MATLAB xyY ?

I have written a code for a color-naming task in which participants will be randomly presented a set of 12 stimuli and will be asked to report whether the stimulus is green or blue. I display colored squares for this purpose by using the Screen command. I wanted to ask whether it is possible to directly implement colours in xyY colour without converting to RGB.

Thanks in advance.

Answer 1

[Walter Roberson]

"I wanted to ask whether it is possible to directly implement colours in xyY colour without converting to RGB."

No, it is not. MATLAB just sends pixel data to the graphics libraries; it does not have any control over how those pixels are converted into light.

xyY is a model of how humans would perceive theoretical light; it does not deal how to generate light from a real system such that the light actually generated matches the desired properties.

If you are working with perception models to that degree then you should be using calibrated displays and setting up hardware profiles to meet your targets. That might call, for example, for using one of the Eizo self-calibrating displays

[matpsyc]

Thanks a lot.

As you also suggested, I use a calibration device to match with the desired properties. I actually wanted to ask whether it is possible to use xyY values as elements in the three-element row vector in MATLAB so that it specifies the colour I want to display without using the equations for conversion. As I understand from your answer, it is not.

Thanks again for your answer.

[Walter Roberson]

Your question is really more one about Psychtoolbox as Screen() is part of that rather than part of MATLAB . Screen() with 'fillrect' only takes rgb or rgba; see http://docs.psychtoolbox.org/FillRect

You might want to look at RenderDemo which puts up an xyY patch.

[Stephen23]

Of course you could use MATLAB to specify the xyY values that you want to display, even if you have to write the toolbox yourself. It is not very likely that you will find any monitor or TV that accepts xyY input though, so you will have to anyway convert to sRGB, or YCbCr, or some other supported color encoding.