Robust Image Watermarking against Brightness and Contrast Change

The brightness and contrast changes are common image processing, so a robust watermarking algorithm against them is presented based on image edge detection in this article. Firstly Prewitt operator is used for image edge detection. Secondly watermark is embedded into the gradient amplitude and direction of the edge point. The invisibility of our algorithm is better for the masking effect of human vision. And the robustness is also better for the stability of the edge.