Filling some region with colour, and the rest of the image as black

Question

I have drawn some polygon on an image after using imshow and hold on, and filled it with white as follows:

fill(x(k),y(k),[1 1 1])

How can I make the rest of the image black while keeping the polygon white? In other words, how can I make a binary image, where the polygon is white, and the rest of the image is black? Provided that the polygon is a bit complex.

Thanks.

Answer 1

Use roipoly:

BW = roipoly( I, x(k), y(k) );

Where I is your input image (you only need it to get the desired output size of the binary maxk BW). y and x are the corners of your polygon.