MATLAB: Please help me run this code, as i am unable to solve an error.

#single errorImage Processing Toolbox

%clc, clear, close all
A = imread('image.jpg');
R = A(:, :, 1);
G = A(:, :, 2);
B = A(:, :, 3);
[m,n] = size(A);
total = m*n;
color = zeros(total,3);
freq = zeros(total);
index = 1;
for i = 1:172
    for j = 1:276
        X(1) = R(i,j);
        X(2) = G(i,j);
        X(3) = B(i,j);
        if i==1 && j==1
            color(index,1) = X(1);
            color(index,2) = X(2);
            color(index,3) = X(3);
            freq(index) = 1;
            
        else
           k = index;
           while k >= 1
               if color(k,1)== X(1) && color(k,2)== X(2) && color(k,3)== X(3)
                   freq(k) = freq(k)+1;
                   break;
               end
               k = k-1;
           end
           if k < 0
               index = index + 1;
               color(index,1) = X(1);
               color(index,2) = X(2);
               color(index,3) = X(3);
               freq(index) = 1;
           end
               
         end
    end
end
C = sort(freq, 'descend');
fprintf('\n');
fprintf('\t Number \t Frequency\n');
for i = 1 : index
    fprintf '('color(i,1)','color(i,2)','color(i,3)' = 'freq(i)'\n' ;
end

Best Answer

There are a few issues with your code:
  • you correctly query the size of your image and use that to preallocate your arrays, then you throw that out of the window and have hardcoded values for the loops of your bound. If the input image is not exactly 172x276 your code will either error (smaller image) or miss some pixels (larger image).
  • you have a while loop that ends when k reaches 0. So the subsequent if k < 0 is guaranteed to never be true. As a result, you never increment i and never store new colours.
  • Not sure why you're sorting the frequency. You never use C anyway. And you can't sort the frequency without rearraging your color array at the same time.
  • Your fprintf statement is completely wrong. 
fprintf('(%d, %d, %d) = %d\n', color(i, 1), color(i, 2), color(i, 3), freq(i));  %assuming color is uint8 or uint16
Of course, the whole code is very inefficient and it's probably going to be very slow. If you want to search an array for some values, use ismember rather than coding your while loop.
The whole thing could be coded very simply with:
img = imread('image.jpg');
pixels = reshape(img, [], 3);  %reshape the image as a Mx3 array where M is the number of pixel and columns are R, G, B respectively
[colours, id] = unique(pixels, 'rows');   %get unique colour, and assign unique id to each
freq = accumarray(id, 1);   %calculate histogram of ids
fprintf('(%03d, %03d, %03d) = %d\n', [colours, freq]');
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