How do I check if a value is a correct color?

Whether there is a function like

logical = isvalidcolor(value)

to check if some value may be used like a color (one of values specified in ColorSpec e.g.)

Answer 1

[Image Analyst]

Not that I'm aware of - there's just not that much need - though you could write one if you want.

[Ivan]

Thanks a lot!

But I have hoped I will not write this ))

[Image Analyst]

If it's not 'r', 'b', and so on, what will you do? Announce an error? Well whatever function you'd pass the "bad" color code into will announce an error also, so why do you need to do it also?

[Ivan]

It's a good question! I havn't known about announcing an error by uicontrol or some else.

[Image Analyst]

You could do something like

message = sprintf('%s is an invalid color.  Please use r, g, b, y, m, c, k, or w', theirColor);
uiwait(warndlg(message));
return;

Answer 2

[Tommy]

Once I needed this function to suppress error messages, by setting wrong color values to MATLAB default. I used:

function logical_out = iscolor( color )
color = lower(color);
logical_out=(isnumeric(color) && (sum(size(color)==[1 3])==2 || ...
  sum(size(color)==[3 1])==2) && sum((color<=[1 1 1] & ...
  color>=[0 0 0]))==3) || sum(strcmpi({'y','m','c','r','g','b','w','k',...
  'yellow','magenta','cyan','red','green','blue','white','black'},color))>0;
end

Hope this helps.

[Image Analyst]

I'd add as the first line

color = lower(color);

It will make it more robust by handling upper case characters and words also.

[Tommy]

Thanks! I adapted it.

[Rick Coon]

Actually, doesn't using strcmpi eliminate the need to use color = lower(color); ?

[Image Analyst]

Yes. Maybe he adapted that part also after my comment.

[Grzegorz Lippe]

Well that helps until that point somebody specifies the color as hexadecimal value or integer from 0 ...255. Hope mathworks creates a validate color function :/

[Paul Wintz]

Matlab 2020b has a validatecolor function.

Answer 3

[Paul Wintz]

In Matlab 2020b and later, use the validatecolor function.