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

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;

Answer 1

[Guillaume]

'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

Answer 2

[Ataur Rahman]

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

check my code. It is working