Color Image Watermarking Based on DS-CDMA Using Hadamard Kernel

For gray level images, watermarking algorithms based on image normalization and DS-CDMA have been proposed. In DS-CDMA method, a binary pseudo-random sequence is generated and embedded as a watermark. In the extracted binary pseudo-random sequence, we may see the non-zero Bit Error Rate (BER) even if the watermarked image has not been attacked. We extend this method to color images. The Hadamard kernel is used for improving the BER against no attack. Experimental results show that our method guarantees the zero BER against no attack and the robustness against common image processing attacks such as JPEG compression, cropping, scaling, histogram equalization, changing luminance and contrast, etc.