Abstract: A new technique combining spatial domain and frequency domain is proposed, which can provide more watermarks in the condition of reducing the distortion of watermark image. The watermark is divided into two parts: the spatial domain and the frequency domain, and embedded into the spatial domain and the frequency domain according to the user's needs or the importance of the data respectively. Experimental results provide the comparisons when different sized watermarks are embedded into the grayscale image. The proposed combinational image watermarking possesses the following advantages. More watermark data can be embedded into the host image, so that the capacity is increased. The watermark is divided into two parts in spatial domain and frequency domain makes the degree of protection double. The splitting strategy can be designed to be more complex in order to make the embedded watermark unrecoverable. In addition, in order to enhance the robustness, a random permutation of the watermark is used to combat the attacks of signal processing such as image crops.

Key words: Image processing, Image watermarking, Compression, Security, Encryption, Signal processing

摘要： 提出了一种将空间域和频率域相结合的新技术,可以在减少水印图像失真的前提下,提供更多的水印。将水印分成空间域和频率域两部分,并根据用户的需求或数据的重要性分别嵌入空间域和频率域。当将不同大小水印嵌入到灰度图像时,提出的组合图像水印具有以下优点:可以将更多的水印数据嵌入到宿主图像中,从而提高水印容量;将水印分为空间域和频率域两部分,使保护的程度加倍;为了使嵌入的水印无法恢复,可以将划分策略设计得更复杂。此外,为了增强鲁棒性,用水印的随机置换来对抗图像裁剪等信号处理的攻击。

关键词: 图像处理, 图像水印, 压缩, 安全, 加密, 信号处理