please help me run this code, as i am unable to solve an error.

%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

[dpb]

Well, we're pretty-much stuck since don't have your input file and you don't even give a hint as to what the error is or where...

[harsh vimal]

Actually, there is no real error but i am not getting the desired output, and as for the input file, it is simply any image.

The output i need is, the RGB triplet should come with the no. of times they have occured in an image i.e., frequency of RGB triplets. I have done the coding for the logical part but i am not able to display it, so now maybe you can help.

[Walter Roberson]

You need the two output version of sort()

[Image Analyst]

Again, you forgot to attach image.jpg. Is it proprietary/secret or something?

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Answer 1

[Guillaume]

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]');

[harsh vimal]

Thank you, your answer is very helpful and i am able to proceed with my code. Just one last thing, if you can help me sort the frequency according to my code.

[Guillaume]

If you sort the frequency, you also need to keep track of which order you sort them in, so, as walter said in a comment, you have to use the two output version of sort:

[sortedfreq, order] = sort(freq);
color = color(order, :);