function f = convolution(fileinput,filemask)
input = imread(fileinput);
masko = imread(filemask);
[rows cols] = size(input);
[rowms colms] = size(masko);
mask = zeros(rowms,colms);
%flip the mask
for r = 1:rowms
    for c = 1:colms
        mask(r,c) = masko(rowms-r+1,colms-c+1);
    end
end
%convolve mask with image  using the equation from slides
output = zeros(rows,cols);
for r = 1:(rows-rowms)
    for c = 1:(cols-colms)
        for rm = 1:rowms
            for cm = 1:colms
                
                    output(r,c) = output(r,c) + double(input(r+rm,c+cm))*double(mask(rm,cm));
                
            end
        end
    end
end
% setting pixels out of range to 0, ie as 'wrong'
for r = (rows-rowms):rows
    for c = 1:cols
        output(r,c) = 0;
    end
end
for r = 1:(rows-rowms)
    for c = (cols-colms):cols
        output(r,c) = 0;
    end
end
%contrast the output
max = 0;
min = output(1,1);
for r = 1:rows
    for c = 1:cols
        if output(r,c) > max
            max = output(r,c);
        end
        if output(r,c) < min
            min = output(r,c);
        end
    end
end    
ratio = double(max-min)/double(255);
for r = 1:rows
    for c = 1:cols
        if output(r,c) ~= 0
            tmp = output(r,c);
            output(r,c) = double(tmp-min)/double(ratio);
            output(r,c) = round (output(r,c));
        end
    end
end
max
min
maxk=0;
mink=output(1,1);
for r = 1:rows
    for c = 1:cols
        if output(r,c) > maxk
            maxk = output(r,c);
        end
        if output(r,c) < mink
            mink = output(r,c);
        end
    end
end     
f = output;
maxk
mink