Average intensity of an image

Hi, an image is in unit8 or greyscale image and data in I(x_i,y_j) format. How will calculate average intensity of an image without using any function and the expression of avg intensity is:

Answer 1

[KSSV]

A = magic(5) ;
[m,n] = size(A) ;
iwant = 0 ;
for i = 1:m
    for j = 1:n
        iwant = iwant+A(i,j) ;
    end
end
iwant = iwant/(m*n) ;
[iwant mean(A(:))]

ans = 1×2

13 13

[Surendra Ratnu]

But I am getting I_avg = 0. Can you give some suggestion ??

[Surendra Ratnu]

Iwant have only constant value (=255) in every step

[DGM]

If you're going to commit to doing things the hard way, you'll have to also commit to paying extra attention to variable class. If the image is an integer-class array (e.g. uint8), then the accumulated sum will also be implicitly uint8. It will immediately be truncated, so the sum will never exceed 255. In all probability, the product of the page geometry (i.e. m*n) will be much larger than 255, so the division step will round to a mean of 0, since that's the closest integer.

Make sure A is of an appropriate class.

A = double(A);

[KSSV]

@Surendra Ratnu I have thought about this question while answering. I left it for you to figure out. Any ways you have the answer from @DGM