how to divide an image diagonally into two part?

i want to divide an image diagonally,into two equal part. how can i do this?

Answer 1

[Geoff Hayes]

Soumyadip - consider using tril or triu to obtain the lower triangular part or upper triangular part of the image (matrix).

[Soumyadip Chakraborty]

x=imread('12.jpg');
x1=size(x)
x1=
 168 300 3

then how can i apply tril/triu on it to get the diagonally divided image?

[Image Analyst]

What do you want? Do you want a 1-D list of all pixels values in each triangle? Or do you want a masked image where half the image is the original, and half is set to some value, like black (0) or white (255)?

Answer 2

[Image Analyst]

Not exactly sure what you mean so I did it two different ways, one to give a masked image and another that has a 1-D list of extracted values. Make note that the pixels along the main diagonal will occur in both the upper and lower images.

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

grayImage = imread('cameraman.tif');
% Display the original gray scale image.
subplot(3, 1, 1);
imshow(grayImage, []);
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') 

upperPixelImage = triu(grayImage); % 2D image
% Display the original gray scale image.
subplot(3, 1, 2);
imshow(upperPixelImage, []);
title('Upper Triangle', 'FontSize', fontSize);

% Get the 1-D list of upper values.
mask = triu(ones(size(grayImage))) > 0;
upperList = upperPixelImage(mask);

lowerPixelImage = tril(grayImage); % 2D image
% Display the original gray scale image.
subplot(3, 1, 3);
imshow(lowerPixelImage, []);
title('Lower Triangle', 'FontSize', fontSize);

% Get the 1-D list of lower values.
mask = tril(ones(size(grayImage))) > 0;
lowerList = lowerPixelImage(mask);

[Nepoleon Keisham]

Thank you for your help but Triu is Tril works only on square matrix. Please help in finding the diagonal half of an image or a matrix, where the size of rows and column are different.