Image Processing/Matrix Math Question

Hello,

I have an m-by-n matrix of numerical values which correspond to weighting factors (essentially intensities) applied to each point (x,y) in an x-y coordinate system. What I would like to do is apply a function f(x,y) to each point (x,y) and then multiply the function by the weighting factor. This would hopefully result in another m-by-n matrix. In addition, I would like to sum up the values of the resulting matrix.

I would appreciate any help on this problem.

Thank you much,

John

Answer 1

[Image Analyst]

That is exactly what the nlfilter() functions does. Here's your demo:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;

A = imread('cameraman.tif'); 
[rows columns] = size(A);
A = im2double(A);
fun = @(x) median(x(:)); 
B = nlfilter(A,[5 5],fun); 
subplot(2,2,1);
imshow(A)
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 

% Display image B
subplot(2,2,2);
imshow(B)
title('Function applied to image', 'FontSize', fontSize);

% Get array of weights the same size as the image.
weights = peaks(256);
weights = weights - min(weights(:)); % Make all positive.
subplot(2,2,3);
imshow(weights, [])
title('Our weights', 'FontSize', fontSize);

% Multiply weights by image.
outputImage = weights .* B;
% Display image outputImage
subplot(2,2,4);
imshow(outputImage, [])
title('Now with weights applied', 'FontSize', fontSize);

[John Moseley]

Thank you once again!

John