MATLAB: Write a function called blur that blurs the input image

blurdo not give complete solutionshomeworkno more answers please!!!

Write a function called blur that blurs the input image. The function is to be called like this:
output = blur(img,w);
where img, the input image is a two-dimensional matrix of grayscale pixel values between 0 and 255. Blurring is to be carried out by averaging the pixel values in the vicinity of every pixel. Specifically, the output pixel value is the mean of the pixels in a square submatrix of size 2w+1 where the given pixel sits in the center. For example, if w is 1, then we use a 3×3 matrix, that is, we average all the neighboring pixels of the given pixel and itself. Only use valid pixels when portions of the blurring matrix fall outside the image. For example, the blurred value corresponding to w = 1 at index (1,1) would be the mean of of elements (1,1), (1, 2), (2,1) and (2, 2). Both input img and output output are of type uint8.
You can download the test image here
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to use in MATLAB.
I am using the following code but it gives me an error. Can anyone please tell me where I am going wrong?
function output = blur(img,w)
B=double(img);
[m,n] = size(B);
k=2*w+1;
for i = 1:m
    for j = 1:n
        p=i-fix(k/2);
        q=i+fix(k/2);
        r=j-fix(k/2);
        s=j+fix(k/2);
        if p<1
            p=1;
        end
        if q>m
            q=m;
        end
        if r<1
            r=1;
        end
        if s>n
            s=n;
        end
        A=B([p:q],[r:s]);
        B(i,j)=mean(A(:));
    end
end
output=uint8(B);
end

Best Answer

Your program is correct. But you are overlapping resultant matrix with input matrix which is creating proble.
For e.g. you have calculated avg pixel for w=1 and for location(1,1) which will store at same matrix at location(1,1). But for (1,2) while avg surrounding cells it will consider (1,1) location of matrix B where on location(1,1) you saved your result/output value not input value.
So just create new output matrix like mentioned below. Hope it will help you.
function output = blur(img,w)
B=double(img);
[m,n] = size(B);
k=2*w+1;
for i = 1:m
    for j = 1:n
        p=i-fix(k/2);
        q=i+fix(k/2);
        r=j-fix(k/2);
        s=j+fix(k/2);
        if p<1
            p=1;
        end
        if q>m
            q=m;
        end
        if r<1
            r=1;
        end
        if s>n
            s=n;
        end
        A=B([p:q],[r:s]);
        C(i,j)=mean(A(:));
    end
end
output=uint8(C);
end
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