MATLAB: Detect Colors in a white image

colors

Greetings, for a school project I need to detect if there are nonwhite colors in this image.
http://radar.weather.gov/ridge/RadarImg/N0R/JUA_N0R_0.gif
If there are colors apart from white in the image I need to transmit a signal to a controller telling it to start working.
How do I detect colors and transmit the signal?

Best Answer

in a unsigned 8bit integer image (uint8) (just example)
 I = your_image
assert(isa(I,'uint8'),'For this example I is expected to be uint8');
if(any(I(:)~=255))
   fprintf('There are non white areas');
else
   fprintf('All white!');
end
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