MATLAB Answers

Random square sampling for single channel images

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len Bruce
len Bruce on 28 Dec 2020
Answered: len Bruce on 28 Dec 2020
For a single-channel image with random square sampling, Not a fixed sub-window,how to generate random squares usingMATLAB, an example is as follows,Thank you

Answers (2)

Subhadeep Koley
Subhadeep Koley on 28 Dec 2020
Hi, here is one working example.
Hope this helps!
% Read the original image
img = imread('cameraman.tif');
[row, col, ~] = size(img);
imgSize = [row, col];
% Specify dimension of the random square
squareSize = [50, 50];
% Calculate crop rectangle
maximumPosValue = (imgSize - squareSize + 1);
initialRandomPos = [randi(maximumPosValue(1)), randi(maximumPosValue(2))];
cropRect = [initialRandomPos(2), initialRandomPos(1), squareSize(2)-1, squareSize(1)-1];
% Crop the image
imgCropped = imcrop(img, cropRect);
% Visualize results
out = imtile({img, imgCropped}, 'BackgroundColor', 'w');
figure
imshow(out)
title('Original image | Random cropped image');
  2 Comments
Subhadeep Koley
Subhadeep Koley on 28 Dec 2020
@len Bruce you can randomize the sqare window size like below.
% Read the original image
img = imread('peppers.png');
[row, col, ~] = size(img);
imgSize = [row, col];
% Specify dimension of the random square
val = randi(min(imgSize));
squareSize = [val, val];
% Calculate crop rectangle
maximumPosValue = (imgSize - squareSize + 1);
initialRandomPos = [randi(maximumPosValue(1)), randi(maximumPosValue(2))];
cropRect = [initialRandomPos(2), initialRandomPos(1), squareSize(2)-1, squareSize(1)-1];
% Crop the image
imgCropped = imcrop(img, cropRect);
% Visualize results
out = imtile({img, imgCropped}, 'BackgroundColor', 'w');
figure
imshow(out)
title('Original image | Random cropped image');

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len Bruce
len Bruce on 28 Dec 2020
Generate the coordinates of the image square sampling based on random numbers,such as the upper left and the lower right co-ordinates of the ith random sub-window is denoted by (x1,y1)and (x2,y2)respectively. (image(x1:x2, y1:y2))

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