A new visible watermarking technique applied to CMOS image sensor
Pingping Yu, Yan Shang, Chunming Li · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2013
This paper presents a new visible watermarking solution for CMOS image sensor which can enhance secure features of captured images. Visible watermarks are embedded in the Bayer format image data and can be transferred by the subsequent interpolation process. A piecewise function is setup based on the gray scale resolution characteristics of human eyes. Watermark stretch factor can be adaptively chosen according to the gray value of the current pixel. The advantage of this algorithm is that the watermark has the same visibility in different image brightness region. A number of color images have been used to test the method. In order to check the robustness of watermarked images, we conducted adding noise and filtering experiments, results show that the visibility of watermark is also good after the experiments. The approach allows a digital watermark to be embedded in an image immediately upon its capture, before leaving the imaging chip.