MATLAB function for image filtering - matlab

Question

I'm looking to implement my own Matlab function that can be used to compute image filtering with a 3x3 kernel.
It has to be like this: function [ output_args ] = fFilter( img, mask )
where img is a original image and mask is a kernel (for example B = [1,1,1;1,4,1;1,1,1] )
I'm not supposed to use any in-built functions from Image Processing Toolbox.
I have to use this
where:
s is an image after filter
p is an image before filter
M is a kernel
and N is 1 if sum(sum(M)) == 0 else N = sum(sum(M))
I'm new to MATLAB and this is like black magic for me -_-

Answer 1

This should do the work (Wasn't verified):
function [ mO ] = ImageFilter( mI, mMask )
%UNTITLED2 Summary of this function goes here
% Detailed explanation goes here
numRows = size(mI, 1);
numCols = size(mI, 2);
% Assuming Odd number of Rows / Columns
maskRadius = floor(siez(mMask, 1) / 2);
sumMask = sum(mMask(:));
if(sumMask ~= 0)
mMask(:) = mMask / sumMask;
end
mO = zeros([numRows, numCols]);
for jj = 1:numCols
for ii = 1:numRows
for kk = -maskRadius:maskRadius
nn = kk + 1; %<! Mask Index
colIdx = min(max(1, jj + kk), numCols); %<! Replicate Boundary
for ll = -maskRadius:maskRadius
mm = ll + 1; %<! Mask Index
rowIdx = min(max(1, ii + ll), numRows); %<! Replicate Boundary
mO(ii, jj) = mO(ii, jj) + (mMask(mm, nn) * mI(rowIdx, colIdx));
end
end
end
end
end
The above is classic Correlation (Image Filtering) with Replicate Boundary Condition.