how to set the background color of this image to 0 and remaining foreground color to 1 to make this image binary?

Answer 1

[Image Analyst]

Make a mask:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Now make the mask
mask = ~(recChannel ~= 0 & greenChannel == 0 & blueChannel == 0);

[Arshad Ali]

if the image is like this, then the code will be the same.

[Image Analyst]

Your colors are not pure.

When I tried to save the image it looks like this is a labeled image returned from the watershed function, so you should already have the binary image to begin with, so that is what you want. You can also get it from the labeled matrix like

binaryImage = labeledMatrix ~= 0;

but that should not be necessary. Not sure how the white boundary lines got there though.