Abstract：To solve the problems of low watermark capacity and bad robustness of digital watermarking algorithm for color images, a method was proposed based on blocks and NSCTSVD. The color image was divided into three channels of R, G and B, and the three channels were respectively broken down into four nonoverlapping blocks. NSCT was applied to the nonoverlapping blocks for achieving the lowfrequency part of each block, and SVD was applied to every lowfrequency part. SVD was also applied to the three channels of R, G and B of color watermark images. Considering the principle that the robustness and invisibility of watermark could be well balanced, the optimal watermark embedding factor was selected. The singular value of R, G and B of watermark was added to the singular value of lowfrequency part of each block of original image to embed watermark information. The experimental results show that the proposed algorithm has good transparency and robustness for many attacks of noise, filtering, cropping, JPEG compression and rotation.
张倩倩, 詹永照, 林涵阳. 基于分块和NSCTSVD的彩色图像数字水印算法[J]. 江苏大学学报（自然科学版）, 2017, 38(5): 582-589.
ZHANG Qian-Qian, ZHAN Yong-Zhao, LIN Han-Yang. Digital watermarking algorithm for color images based on blocks and NSCTSVD[J]. Journal of Jiangsu University(Natural Science Eidtion)
, 2017, 38(5): 582-589.
2017, Vol. 38 
