New Digital Watermarking for Few-Color Images

In this paper, we propose a new digital watermarking algorithm named spatial unified key insertion (SUKI) for few-color images. By performing the adaptive threshold halftoning and contour shaping and modification, we can embed a binary logo into a digital image with superior JPEG compression resistance ability. The bit error rate (BER) of JPEG attack is equal to zero for all testing images with quality factor≥80. The BER is much lower than the traditional watermarking algorithms, such as spread spectrum watermarking and quantization index modulation watermarking. The payload is considerably high and there are no "salt-and-peppers" artifacts in the watermarked images. No additional color is introduced and the palette keeps unchanged after watermark embedding. The proposed algorithm can be applied to natural images with distinct boundaries by segmenting the images into different parts.