Color image watermarking using selective MSB-LSB embedding and 2D Otsu thresholding
Thien Huynh‐The, Sungyoung Lee · 2017
This paper proposes a novel digital image water-marking method, namely SMLE, that allows to intelligently embed a gray-scale watermark image into a color host image in the wavelet domain. By decomposing a gray-scale image to binary images in digits ordering from Least Significant Bit (LSB) to Most Significant Bit (MSB), binary bits are efficiently embedded to optimal wavelet coefficient blocks using a quantization technique which encodes wavelet coefficient differences to either of two pre-identified thresholds for corresponding 0-bits or 1-bits. To boost visual quality, an embedding rule is improved by equal spreading coefficient adjustment on two middle-frequency sub-bands instead of only one as existing approaches. Additionally, 2D Otsu algorithm, more proficient than 1D Otsu algorithm for binary classification under attacking scenarios, is modified to flexibly calculate an optimal threshold for high-rate watermark extraction. According to experimental results, our proposed SMLE watermarking model produces remarkable impercepti-bility as well as high robustness against common digital image transformations and mostly does better than other existing methods at same payload rate.