What do you mean? The density is 100% isn't it? Let's say your silhouette is this:
1 1 1 1 1
1 0 0 0 1
1 0 0 1 1
1 1 1 1 1
The zeros are the dark silhouette and the 1's are the light background. The "density" of the silhouette, or the number of zeros in the area that has zeros is 100% isn't it? How do you define density? Is it optical density, like the gray level, or is it something per unit area? Try reading this: http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer
