problem with calculation of percentage of colormap

i want to calculate the percentage of high amount of "red" in an image of a colormap. what should be the equation i should input? 'stress' is a colormap image.

[image_1x image_1y] = size(stress);

for x = 1:image_1x
   for y = 1:image_1y
       if(stress(x,y) <=250) || (stress(x,y) >=255)
           //???
       end
   end
end

Answer 1

[Teja Muppirala]

You don't need to loop over every element one by one to do this. MATLAB is very good at doing operations on entire matrices in one command. You can simply write

L = 55; % Pick a level
percent_over = 100 * nnz(I > L) / numel(I)

This is basically counting the number of elements greater than L, and dividing it by the total number of elements in the image.

You can replace L with whatever value you would like to use (from your picture, "red" seems to be anything above about 50).

[joanna]

How do i convert the number into string and input it on the static text?

[Image Analyst]

caption = sprintf('The number = %.3f', theNumber);
set(handleToStaticTextControl, 'String', caption);