A Modified Kernels-Alternated Error Diffusion Watermarking Algorithm for Halftone Images
Digital Halftoning is the rendition of continues-tone images on two-level displays. A modified kernels-alternated error diffusion (KAEDF) watermarking algorithm for halftone images is presented in this paper, which can achieve relatively large embedding rate with good visual quality and high robustness. With the introduction of threshold modulation in error diffusion, the proposed algorithm greatly eliminates the edge sharpening and noise shaping distortion of the watermarked halftone image due to the conventional error diffusion algorithm. Consequently, more spectral distribution features in DFT domain characterized with the two alternated kernels, i.e., Jarvis and Stucki, are preserved in the resulting watermarked halftone image, which greatly improves the performance of watermark decoding. Instead of the original grey level image, the one generated with the inverse halftone algorithm is utilized to determine the local threshold for blind watermark detection. Extensive simulations are carried out, which demonstrates that the modified KAEDF watermarking algorithm achieves significant improvements in performance of visual quality and watermark decoding rate.
KeywordsVisual Quality Watermark Image Watermark Algorithm Contrast Sensitivity Function Threshold Modulation
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