How can I create a binary image, where the blue pixels are white and everything else is black?

I have an image where there is a light-blue book in the background. I need to create a binary image where I select only the blue pixels of the image as white and everything else as black so I can 'isolate' the book.

Answer 1

[Image Analyst]

Use the Color thresholder on the Apps tab of the tool ribbon. Then export the function to an m-file. Or you might try this

redChannel = rgbImage(:, :, 1);
binaryImage = redChannel < 128; % Adjust value as needed.
% Extract largest blob only
binaryImage = bwareafilt(binaryImage, 1);

This assumes the rest of your image is some uniform non-blue color. If the "foreground" and the rest of your "background" (not including the book in the background) is cluttered with all kinds of various objects, then it could be very challenging. In that case, attach your image to your original post up top.

[ESIDOR PASHAJ]

This answer helped me a lot. Thank you very much. :)