how to get random pixel index from binary image with value 1 ?

I have a binary image of large size (256x256). In this image most of the pixel values are zero and some of them are 1. I need to get only 100 randomly chosen pixel coordinates with value 1 from image.

Answer 1

[Guillaume]

pixels = [ones(1, 100), zeros(1, 256*256-100)];
img = reshape(pixels(randperm(numel(pixels))), 256, 256);

[Ahlam Benahmeida]

can you help me please, if I have a color image and I want to extract the random pixels value and save them in a new matrix?

[Walter Roberson]

num_needed = 100;
[rows, cols, panes] = size(YourImage);
selected_indices = randperm(rows * cols, num_needed);
[r, c] = ind2sub([rows, cols], selected_indices(:));
random_pixel_r = YourImage(r, c, ones(num_needed,1));
random_pixel_g = YourImage(r, c, 2*ones(num_needed,1));
random_pixel_b = YourImage(r, c, 3*ones(num_needed,1));
random_new_image = cat(3, random_pixel_r, random_pixel_g, random_pixel_b);