Image Processing along diagonal. I am a student and beginning learner of matlab, I have study some code and do not understand the meaning also the syntax of the code(the second for loop), can anybody help me? Thank you.

I = imread('lenna.tiff');   % read the image to variable I
[x y z]=size(I);               % read image size to variable x, y, z
R=zeros(x,y,z);              % initialize the result matrix
% copy the original block of data
for n = 1:x
  R(n,1:n,:)=I(n,1:n,:);
end
% copy the inverted block of data
for n = 1:x
  n
  R(1:n,n,:)=I(n,1:n,:);
end
R=uint8(R);                     % convert it to unsiged integer
imshow(R);                     % display the image

Answer 1

[Image Analyst]

That is ridiculous code - wasteful and repetitive. I recommend that you run fast and far away from that code and not use it. And whoever wrote it needs to take a refresher course in MATLAB programming. Instead you should look at the examples in the help documentation or check out my File Exchange.

[Trevor]

The code were given by the teaching associate in the university. He gave this sample for us to self learning and wants us to do a Kaleidoscope. I still haven't got any idea >_<, do you know any websites have matlab sample code about kaleidoscope that can give me a reference. I can't find any. <http://3.bp.blogspot.com/-dXAgV1Rea_M/T2o2nhrd2fI/AAAAAAAAAC8/p3uWgA2w-Kc/s1600/kaleidoscope-view.jpg>Thanks.

[Image Analyst]

Well I guess it does do that. Perhaps if we rename some variables and put in some comments it will help you understand.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;

I = imread('peppers.png');   % read the image to variable I
[Rows columns numberOfColorChannels]=size(I);               % read image size to variable x, y, z
% Crop to a square
I = I(1:Rows, 1:Rows, :); % Assumes x < y.
[Rows columns numberOfColorChannels]=size(I); % Get new square dimensions.
R=zeros(Rows,columns,numberOfColorChannels);              % initialize the result matrix
subplot(2, 2, 1);
imshow(I);
title('Original Image', 'FontSize', fontSize);
% Copy a triangle from the original image.
for n = 1:Rows
  R(n,1:n,:)=I(n,1:n,:);
end
subplot(2, 2, 2);
imshow(uint8(R));
title('Initial half of the R Image', 'FontSize', fontSize);
% Paste the triangle into the other triangle.
for n = 1:Rows
  n
  R(1:n,n,:)=I(n,1:n,:);
end
R=uint8(R);                     % convert it to unsiged integer
subplot(2, 2, 3);
imshow(R);
title('Final R Image', 'FontSize', fontSize);

% Go all the way around
R360 = [R imrotate(R, 270); imrotate(R, 90) imrotate(R, 180) ];
subplot(2, 2, 4);
imshow(R360);
title('R360 Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);