how to crop image to 512x512 pixel

i have some image that i want to crop all the image into 512x512 pixel and make it in different spot or location in an image.

how to make each image 20 ROI, each image collect roi not at same spot.

1. Size roi 512x512 pixel

2. Different spot/ location in an image

Answer 1

[Image Analyst]

OK, seems you must have encountered some difficulty with my other answer. So here is what I've done for you. Is it what you want?

% Demo by Image Analyst
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 25;
fprintf('Beginning to run %s.m ...\n', mfilename)

rgbImage = imread('peppers.png');
rgbImage = imresize(rgbImage, 2.5); % Make it at least 512 rows
[rows, columns, numberOfColorChannels] = size(rgbImage)

for k = 1 : 20
	topRow = ceil(rand * (rows - 512));
	leftColumn = ceil(rand * (columns - 512));
	croppedImage = rgbImage(topRow : topRow + 511, leftColumn : leftColumn + 511, :);
	subplot(5, 4, k);
	imshow(croppedImage);
	axis('on', 'image');
	caption = sprintf('Row=%d, Col=%d', topRow, leftColumn);
	title(caption);
	drawnow;
end
g = gcf;
g.WindowState = 'maximized'
fprintf('Done running %s.m.\n', mfilename)

[ctwawa]

how to Make each ROI to be file image because later i wants to load ROI image to call function glcm to extract stat features and color features

[Image Analyst]

Use imwrite()

imwrite(croppedImage, fileName);

[ctwawa]

so i only have to add imwrite (croppedImage, fileName) at the coding at which line or i have to do another one?

[Image Analyst]

Do it anywhere in the loop, such as right after where croppedImage was created. Be sure to make a filename for the cropped image, which probably should be in a different folder.

[ctwawa]

How to load ROI image to call function glcm to extract stat features and color features?

[Image Analyst]

If the image is on disk, you can use imread().

Answer 2

[Image Analyst]

How do you want to specify the starting and ending rows and columns? Or do you want to do it interactively (like with ginput)? Basically, once you know, it's

croppedImage = rgbImage(topRow : topRow + 511, leftColumn : leftColumn + 511, :);

so you just need to define topRow and leftColumn.