How can I crop a picture automatically to get exactly only the Rubik's cube, despite its location or proximity in the image? I am using MATLAB. My aim is to click the picture

Answer 1

[Image Analyst]

What I'd do is to convert to hsv color space, threshold on the S channel, fill regions, then take the convex hull of the region(s) then take the largest single blob. Something like

hsvImage = rgb2hsv(rgbImage);
sImage = hsvImage(:, :, 2);
mask = sImage > 0.25;
mask = imfill(mask, 'holes');
mask = bwconvhull(mask, 'objects');
mask = bwareafilt(mask, 1);

[Sang]

Still not quite what I mean. My idea is how can I cut the Rubik's Cube as shown below

[Image Analyst]

Did you actually try it? See attached full demo. It produces this: