How can i measure reflection of light from plastic or paper images using cam ?

I am writing a code to capture image of paper/plastic objects using logitech cam. I am able to connect take pictures, but i want to distinguish plastic & Paper images based on their reflection index or any other property which is related to reflection of light.. Need help.

Thank You

Answer 1

[Image Analyst]

Take the mean gray level then threshold.

if mean2(grayImage) > someValue
    % It's plastic
else
    % It's paper
end

If you need more help, then say why that didn't work and attach a paper image and a plastic image, after you read this link.