Random square sampling for single channel images

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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
len Bruce
len Bruce on 28 Dec 2020
Very good, but your square sampling is a set fixed window size, what I want is to generate a square area based on the coordinates of the image formed by random numbers,the sampled square area appears randomly in the image and square size is variable,such as image(x1:x2, y1:y2)
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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