MATLAB: How to make a light color features to become bright

Question

good day i have an image with extracted blood vessels and with no noise and a complete figure with all vessels in it..but some of my vessels are light in color..is there a way to make it dark.my image is..

expected output image is (this is image is a manualy drawn image form DRIVE data set

original vessels are

Answer 1

grayImage(binaryImage) = 0; % Set white pixels to black.
grayImage(binaryImage) = 0.5 * grayImage(binaryImage); % Set white pixels to half intensity.