Thodi Diljith M, Rodríguez Jeffrey J
Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ 85721-0104, USA.
IEEE Trans Image Process. 2007 Mar;16(3):721-30. doi: 10.1109/tip.2006.891046.
Reversible watermarking enables the embedding of useful information in a host signal without any loss of host information. Tian's difference-expansion technique is a high-capacity, reversible method for data embedding. However, the method suffers from undesirable distortion at low embedding capacities and lack of capacity control due to the need for embedding a location map. We propose a histogram shifting technique as an alternative to embedding the location map. The proposed technique improves the distortion performance at low embedding capacities and mitigates the capacity control problem. We also propose a reversible data-embedding technique called prediction-error expansion. This new technique better exploits the correlation inherent in the neighborhood of a pixel than the difference-expansion scheme. Prediction-error expansion and histogram shifting combine to form an effective method for data embedding. The experimental results for many standard test images show that prediction-error expansion doubles the maximum embedding capacity when compared to difference expansion. There is also a significant improvement in the quality of the watermarked image, especially at moderate embedding capacities.
可逆水印技术能够在不损失宿主信号任何信息的情况下，将有用信息嵌入宿主信号中。田氏差分扩展技术是一种用于数据嵌入的高容量可逆方法。然而，该方法在低嵌入容量时会出现不良失真，并且由于需要嵌入位置映射图而缺乏容量控制。我们提出一种直方图平移技术作为嵌入位置映射图的替代方法。所提出的技术在低嵌入容量时提高了失真性能，并缓解了容量控制问题。我们还提出了一种称为预测误差扩展的可逆数据嵌入技术。与差分扩展方案相比，这种新技术能更好地利用像素邻域中固有的相关性。预测误差扩展和直方图平移相结合，形成了一种有效的数据嵌入方法。许多标准测试图像的实验结果表明，与差分扩展相比，预测误差扩展使最大嵌入容量增加了一倍。水印图像的质量也有显著提高，尤其是在中等嵌入容量时。
