MATLAB: How to stretch an image by a factor along the horizontal axis

image processingImage Processing Toolboximage transformstretch image projection undo

Hi everyone,

I'm trying to compensate for projection effects that happened during the off axis recording of an image. The result is an elliptic projection instead of a regular circle. So I'm looking for a way to stretch that image along the horizontal axis by a certain factor. How can this be done? Any advice is appreciated. Thanks.

Best Answer

Sure, just send in a new XData property to imshow:

grayImage = imread('moon.tif');
[rows columns numberOfColorChannels] = size(grayImage);
subplot(2, 1, 1);
imshow(grayImage);
newWidth = [1 5 * columns]
subplot(2, 1, 2);
imshow(grayImage, 'XData', newWidth);

If you want to change the actual image itself, rather than just how it appears during display, then you can use imresize()

stretchedImage = imresize(grayImage, [rows newWidth]);

Related Solutions

MATLAB: How to stretch image horizontally and save it

newWidth needs to be a single integer, not a 1-by-2 array of floating point numbers. This works:

Img=imread('cameraman.tif');
[rows, columns, numberOfColorChannels] = size(Img);
subplot(2, 1, 1);
imshow(Img);
newWidth = round(0.592013 * columns)
subplot(2, 1, 2);
stretchedImage = imresize(Img, [rows newWidth]);
imshow(stretchedImage);

MATLAB: Exchange bit-planes

Here's one way:

% Demo to extract and swap bitplanes in a gray scale image.
clc;    % Clear the command window.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;
% Read in a standard MATLAB gray scale demo image.

folder = fullfile(matlabroot, '\toolbox\images\imdemos');
button = menu('Use which demo image?', 'CameraMan', 'Moon', 'Eight', 'Coins', 'Pout');
if button == 1
	baseFileName = 'cameraman.tif';
elseif button == 2
	baseFileName = 'moon.tif';
elseif button == 3
	baseFileName = 'eight.tif';
elseif button == 4
	baseFileName = 'coins.png';
else
	baseFileName = 'pout.tif';
end
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
	% Didn't find it there.  Check the search path for it.
	fullFileName = baseFileName; % No path this time.
	if ~exist(fullFileName, 'file')
		% Still didn't find it.  Alert user.
		errorMessage = sprintf('Error: %s does not exist.', fullFileName);
		uiwait(warndlg(errorMessage));
		return;
	end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage);
% Display the original gray scale image.

subplot(2, 1, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Get the 3rd bitplane
bitPlane3Image = bitget(grayImage, 3);
% Get the 5th bitplane
bitPlane5Image = bitget(grayImage, 5);
% Make the 3rd bitplane the 5th one.
grayImage = bitset(grayImage, 3, bitPlane5Image);
% Make the 5th bitplane the 3rd one.
grayImage = bitset(grayImage, 5, bitPlane3Image);
% Display the original gray scale image.
subplot(2, 1, 2);
imshow(grayImage, []);
title('Modified Grayscale Image', 'FontSize', fontSize);
fprintf('Done running %s.m.\n', mfilename);
msgbox('Done with demo');

Best Answer

Related Solutions

MATLAB: How to stretch image horizontally and save it

MATLAB: Exchange bit-planes

Related Question