How do i write a histogram code without the built in functions ?

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nissrine Neyy 2021-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/785131-how-do-i-write-a-histogram-code-without-the-built-in-functions

评论： nissrine Neyy 2021-3-27

I want to creat a histogram code, knowing that it'll be counting the number of occurence of 3 values of a pixel.

the idea is i have 3 matrices (L1im, L2im, L3im) representing information extracted from an image, size of each of them is 256*226, and i want to compute how many times a combination of let's say (52,6,40) occures (each number correspends to a matrix/component but they're all of the same pixel)

for i = 1 : 256
    for j = 1 : 256
        for k = 1 : 256
            if  (L1im == i) &  (L2im == j) & (L3im == k)
                myhist(i,j,k)= myhist(i,j,k)+1;
            end
        end
    end
end

can anyone help please ?

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Answer 1

Image Analyst 2021-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/785131-how-do-i-write-a-histogram-code-without-the-built-in-functions#answer_659866

在 MATLAB Online 中打开

That's obviously not correct. Try this 3 dimensional histogram

[L1im, L2im, L3im] = imsplit(rgbImage) % Optionasl, if you want to do this instead of operating on the RGB image directly in the loop
[rows, columns, numberOfColorChannels] = size(rgbImage)
myhist = zeros(256, 256, 256); % histogram for uint8 where gray levels go up to 255
for col = 1 : columns
    for row = 1 : rows
        r = L1im(row, col);
        g = L2im(row, col);
        b = L3im(row, col);
        myhist = myhist(r, g, b) + 1;
    end
end