For loop stoping mid way with empty array

Hi,

I'm doing a university project with images using guide.

But in my method to determin the mean of an image using a box value, my for loop stops mid way, l becomes [] and i don't know why.

function [ imagemFinal ] = toMeanAluno( imagem, masc )

    aux = idivide(int32(masc), int32(2));

    contador = 0;
    valor = 0;

    imagemFinal = imagem;

    for i = 1+aux:size(imagem,1)-aux
        for j = 1+aux:size(imagem,2)-aux

            for k = i-aux:masc
                for l = j-aux:masc
                    valor = valor + imagem(k,l);
                    contador = contador + 1;
                end;
            end;

            imagemFinal(i,j) = valor / contador;

            valor = 0;
            contador = 0;

        end;
    end;
end

Answer 1

[Image Analyst]

If you want a fully manual version of convolution with no calling conv2() or imfilter(), then see the attached demo code (below these images that it creates).

[Hugo Duarte]

You sir, should be a professor! Unbelievable, never been so much educated in so little time in my life. Would love to atend a class by you (even if it was 8 hours straight) Thank you so much, and i'm sorry for my bad english.

[Image Analyst]

Well I do teach a few classes in our company. We have hired many professors who became disillusioned with academic life - low pay, long hours, political infighting, tenure battles, too much time spent searching for grants or contracts, not as much freedom to research what they want as they had expected, etc. No thanks - not for me. Well, maybe when I retire - who knows? Plus a surprising number of professors can't program - they just think and delegate all the actual hands-on programming to their grad students. Like my son's engineering professor who assigns homework in MATLAB but who barely knows how to use it herself. I like to both think and do.

Thanks for accepting the answer.

Answer 2

[Image Analyst]

It looks like you're trying to do a moving window mean. So why not just do

windowSize = 7; % Whatever
kernel = ones(windowSize)/windowSize^2;
outputImage = conv2(inputImage, kernel, 'same');

or

outputImage = imfilter(inputImage, kernel);

[Hugo Duarte]

Yes i know, but the professor want us to do by our own method...

[Image Analyst]

What does this line intend to do:

aux = idivide(int32(masc), int32(2));

What is idivide()? Is it imdivide() or did you write your own function that you forgot to attach?

Can you please translate these into English so I know what is intended: aux, masc, valor, & contador. From the context, I think valor is sum, and contador is count, and masc might be mask or window or window width, but I still don't know what aux is (auxilliary?) and I want to make sure.

[Hugo Duarte]

you got everything, and yes aux is auxiliar. imagem is image. idivide is the division nearest integer to round down.

[Image Analyst]

What does auxiliar mean? In English Auxilliary mean like "extra" so I'm not sure what it means when you use it.

What values does k take on in "k = i-aux:masc" Let's say you were at pixel (100,100) and the window size was 7 so the half window size was 3. Then k should go from i-3 to i+3. It doesn't look like it does that for you. I'd do

for k = (i-halfWindowSize) : (i + halfWindowSize)

and similar for l (ell).