How to find the mean value of R G B component in an image without using the comment 'mean'

Question

Arya Raj 2015-4-17

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https://ww2.mathworks.cn/matlabcentral/answers/209644-how-to-find-the-mean-value-of-r-g-b-component-in-an-image-without-using-the-comment-mean

回答： Ataur Rahman 2020-8-8

I'm looping through an input image 1 pixel at a time and determining its RGB value. Afterwards i'm trying to find the average RGB value for the image overall. For some reason the averaging portion of my code isnt working.

I = imread(filename);

[len,wid,d] = size(I)

count = 0;

meanR = 0;

meanG = 0;

meanB = 0;

for j=1:len

        for k=1:wid
               meanR = meanR + I(j,k,1);
               meanG = meanG + I(j,k,2);
               meanB = meanB + I(j,k,3);
               count= count+1;
        end
end
meanR1 = meanR/count;
meanG1 = meanG/count;
meanB1 = meanB/count;

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Answer 1

Guillaume 2015-4-17

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编辑：Guillaume 2015-4-17

在 MATLAB Online 中打开

'isnt working though' does not tell us much. At a guess, your image is of type int8 or int16. To know for sure:

whos I

If you add two uint8 whose combined values is greater than 255 then you'll get to 255 since that's the maximum value that can be encoded in 8 bits. Same with uint16 at 65535.

To fix this:

I = double(imread(filename));

If that's not the issue then you need to give more details about isnt working

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Answer 2

Ataur Rahman 2020-8-8

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https://ww2.mathworks.cn/matlabcentral/answers/209644-how-to-find-the-mean-value-of-r-g-b-component-in-an-image-without-using-the-comment-mean#answer_476824

在 MATLAB Online 中打开

function avgrgb=avgpict(img)
    sz=imread(img); %read the image
    pict=double(sz);% convert it to double for calculations
    dim=size(pict); %determine the dimension of the pict
    count=0;meanR=0;meanG=0;meanB=0;%preallocations
    for i=1:dim(1)
        for j=1:dim(2)
            meanR=meanR+pict(i,j,1);
            meanG=meanG+pict(i,j,2);
            meanB=meanB+pict(i,j,3);
            count=count+1;
        end
        meanR1=meanR/count;
        meanG1=meanG/count;
        meanB1=meanB/count;
    end
    avgrgb=[meanR1,meanG1,meanB1] %prints the rgb average value
end