Algorithm to implement Invisible robust watermarking for images

I'm doing a project on invisible robust watermarking for image security. I have to develop algorithm(s) to accomplish following 3 components.

1)Construct watermark that cannot be totally removed from an image. Also i have to come up with an algorithm that provides ownership authenticity.

2)How much watermark is changed in tampered image, if tamperd reconstruct water mark.

3)Identify the percentage (%) of watermark copying done in the forged image.

First of all I couldn't find any source code to embed invisible robust water mark to an image,can anyone help me, can anyone prefer a better algorithm 2 implement my components? Will be a great help if anyone can share source code for me to implement my components.