Robust spatial watermarking technique for colour images via direct saturation adjustment

Most colour watermarking methods are realised by modifying the image luminance or by processing each component of colour space separately. This paper presents a novel and robust colour watermarking approach for applications in copy protection and digital archives. The proposed scheme considers chrominance information that can be utilised at information embedding. This work presents an approach for hiding the watermark into DC components of the colour image directly in the spatial domain, followed by a saturation adjustment technique performed in RGB space. The merit of the proposed approach is that it not only provides promising watermarking performance but also is computationally efficient. Experimental results demonstrate that this scheme successfully makes the watermark perceptually invisible and robust to image processing operations such as general image processing operations (JPEG2000, JPEG-loss compression, lowpass filtering, and medium filtering), image scaling and image cropping.     

彩色图像的量子水印算法

为提高彩色图像的量子水印效果,本文提出一种基于新颖的增强量子描述(NEQR)的彩色图像水印嵌入及提取方法。首先将水印图像的幅度调整为与载体图像同样大小,然后采用NEQR方案将载体图像量子化,将水印图像嵌入到载体图像中。两幅图像独立存在,采用一个辅助比特进行切换。通过对水印图像中像素灰度值的24个量子比特实施相位旋转实现对水印图像的置乱。嵌入的水印图像被置乱后,每个像素的灰度信息为一个均衡的量子叠加态,测量后整幅图像为一个均匀的白噪声。水印图像的提取过程为嵌入的逆过程,只需采用嵌入过程所用算子的共轭转置即可。该方法的优点是,可在将来的量子计算机上运行,水印的嵌入不影响载体图像的视觉效果,且嵌入的水印图像具有很好的安全性。      

Self-conjugate watermarking technique for halftone images

A novel method for hiding visual patterns in a single error diffused halftone image is presented called self-conjugate error diffusion (SCED). The hidden patterns appear on the halftone image when the halftone image is folded or is overlapped with its own rotated version. Simulation results show that the halftone images have good visual quality and the hidden pattern is clearly visible.     

一种鲁棒的彩色图像多功能水印算法

首先转换彩色图像的颜色空间抽取相应的灰度图像,再对灰度图像进行提升小波分解,在分解过程中利用图像压缩操作,引起近半数的小波系数增大,另一半系数减小,基于系数增减特征实现版权水印和消费者数字指纹的同时嵌入,从而获得版权认证和盗版追踪的双重功能。仿真实验表明该算法具有良好的鲁棒性和不可感知性。     

Wavelet-based watermarking for color images through visual masking

In this paper, a wavelet-based watermarking scheme for color images is proposed. The watermarking scheme is based on the design of a color visual model that is the modification of a perceptual model used in the image coding of gray scale images. The model is to estimate the noise detection threshold of each wavelet coefficient in luminance and chrominance components of color images in order to satisfy transparency and robustness required by the color image watermarking technique. The noise detection thresholds of coefficients in each color component are derived in a locally adaptive fashion based on the wavelet decomposition, by which perceptually significant coefficients are selected and a perceptually lossless quantization matrix is constructed for embedding watermarks. Performance in terms of robustness and transparency is obtained by embedding the maximum strength watermark while maintaining the perceptually lossless quality of the watermarked color image. Simulation results show that the proposed scheme is more robust than the existing scheme while retaining the watermark transparency.     

On spatial quantization of color images

Image quantization and digital halftoning, two fundamental image processing problems, are generally performed sequentially and, in most cases, independent of each other. Color reduction with a pixel-wise defined distortion measure and the halftoning process with its local averaging neighborhood typically optimize different quality criteria or, frequently, follow a heuristic approach without reference to any quantitative quality measure. In this paper, we propose a new model to simultaneously quantize and halftone color images. The method is based on a rigorous cost-function approach which optimizes a quality criterion derived from a simplified model of human perception. It incorporates spatial and contextual information into the quantization and thus overcomes the artificial separation of quantization and halftoning. Optimization is performed by an efficient multiscale procedure which substantially alleviates the computational burden. The quality criterion and the optimization algorithms are evaluated on a representative set of artificial and real-world images showing a significant image quality improvement compared to standard color reduction approaches. Applying the developed cost function, we also suggest a new distortion measure for evaluating the overall quality of color reduction schemes.     

一种彩色QR码嵌入彩色图像的数字水印技术

为了更好地保护数字版权,提出了一种将彩色QR(quick response)码嵌入彩色载体图像的数字 水印算法。算法通过Arnold置乱技术对水印信息进行加密与Contourlet-离散余弦变换和奇 异值分解(Contourlet-DCT-SVD)水印技术完成对水印的嵌 入和提取。通过实验验证,本文算法对JPEG压缩攻击、剪切攻击、高斯噪声和椒盐噪声攻击 具有较强的抵抗 能力,对上述攻击后提取的彩色QR码均能正确识别;对任意旋转攻击后提取出的彩色QR码水 印也具有 较高的识别率,具有较好的不可见性和鲁棒性。     

Content protection in grayscale and color images based on robust digital watermarking

The concept of digital rights management architecture for multimedia will be presented in this paper, with focus on robust digital image watermarking, which is able to undergo geometrical attacks performed against the embedded watermarks. Geometrical attacks are still an open problem for many digital watermarking algorithms used in present time. Most of geometrical attacks can be described by using affine transforms. A new approach to improve robustness against geometrical attacks is presented. The discrete Fourier transform and log-polar mapping are used for watermark embedding and for watermark detection. Some attacks against the embedded watermarks are performed and the results are given. Also two modifications, usage of the proposed method as a synchronization template and implementation for the color images, are presented and experimental results are given too.     

傅立叶计算全息数字水印在彩色图像印刷防伪中的应用

设计了一种针对彩色图像打印-扫描过程的基于傅立叶计算全息技术的数字水印系统.在该系统中我们首次提出将傅立叶计算全息数字水印技术应用于彩色图像印刷防伪,并为之设计了相应的提取程序.该系统与目前其他的针对打印-扫描过程的数字水印系统相比,具有抗剪切、盲检测、水印信息量大等特点.在彩色图像印刷防伪方面具有明显的应用前景.     

利用偏振滤波实现黑白和彩色图像增强

本文提出一种利用偏振滤波法实现零频衰减从而获得图像的边缘增强的方法。制作简单,且可连续控制边缘增强图像的对比度。     

Realisation and robustness evaluation of a blind spatial domain watermarking technique

A blind digital image watermarking scheme based on spatial domain is presented and investigated in this paper. The watermark has been embedded in intermediate significant bit planes besides the least significant bit plane at the address locations determined by pseudorandom address vector (PAV). The watermark embedding using PAV makes it difficult for an adversary to locate the watermark and hence adds to security of the system. The scheme has been evaluated to ascertain the spatial locations that are robust to various image processing and geometric attacks JPEG compression, additive white Gaussian noise, salt and pepper noise, filtering and rotation. The experimental results obtained, reveal an interesting fact, that, for all the above mentioned attacks, other than rotation, higher the bit plane in which watermark is embedded more robust the system. Further, the perceptual quality of the watermarked images obtained in the proposed system has been compared with some state-of-art watermarking techniques. The proposed technique outperforms the techniques under comparison, even if compared with the worst case peak signal-to-noise ratio obtained in our scheme.     

A dual color images watermarking scheme based on the optimized compensation of singular value decomposition

This paper proposes a novel watermarking algorithm based on the improved compensation of SVD for embedding the color image watermark into the color host image. Firstly, the watermark bit is embedded into 4 × 4 block by modifying the second row first column and the third row first column elements of U component after SVD. Then, the embedded block is compensated by the improved optimization operation for obtaining higher PSNR and larger threshold T. The embedded watermark is extracted from various attacked images by using the relation between the modified elements of U component without resorting to the original data. Moreover, the proposed algorithm overcomes the problem of false positive detection. The experimental results show that the proposed algorithm not only guarantees the invisibility and robustness of the watermark, but also has better performance than other methods mentioned in this paper.     

基于邻域像素差分矩阵的彩色空域图像隐写分析特征

通过分析灰度空域图像隐写直接扩展至彩色空域图像潜在的安全问题,提出了针对彩色空域图像隐写的隐写分析特征。首先,计算颜色通道内邻域像素差分矩阵的Markov转移概率矩阵,提取颜色通道内特征并进行融合;然后,计算颜色通道间邻域像素差分矩阵的Markov转移概率矩阵,并将水平和垂直共4个方向与对角和反对角共4个方向的转移概率矩阵分别进行融合,作为颜色通道间特征;最后,颜色通道内特征与颜色通道间特征构成最终的隐写分析特征,并使用集成分类器作为特征训练和测试工具。实验结果表明,该隐写分析特征可有效检测彩色空域图像隐写,并且颜色通道间特征能有效捕获内容自适应隐写对彩色图像的颜色通道间相关性的影响。     

数字图像水印研究综述

本文对当前数字图像水印技术的背景、现有方法、发展应用和存在的问题做了一综述,以期进一步推动我国在此前沿领域的研究工作。     

Data hiding watermarking for halftone images

In many printer and publishing applications, it is desirable to embed data in halftone images. We proposed some novel data hiding methods for halftone images. For the situation in which only the halftone image is available, we propose data hiding smart pair toggling (DHSPT) to hide data by forced complementary toggling at pseudo-random locations within a halftone image. The complementary pixels are chosen to minimize the chance of forming visually undesirable clusters. Our experimental results suggest that DHSPT can hide a large amount of hidden data while maintaining good visual quality. For the situation in which the original multitone image is available and the halftoning method is error diffusion, we propose the modified data hiding error diffusion (MDHED) that integrates the data hiding operation into the error diffusion process. In MDHED, the error due to the data hiding is diffused effectively to both past and future pixels. Our experimental results suggest that MDHED can give better visual quality than DHSPT. Both DHSPT and MDHED are computationally inexpensive.     

Partition-based vector filtering technique for suppression of noise in digital color images.

A partition-based adaptive vector filter is proposed for the restoration of corrupted digital color images. The novelty of the filter lies in its unique three-stage adaptive estimation. The local image structure is first estimated by a series of center-weighted reference filters. Then the distances between the observed central pixel and estimated references are utilized to classify the local inputs into one of preset structure partition cells. Finally, a weighted filtering operation, indexed by the partition cell, is applied to the estimated references in order to restore the central pixel value. The weighted filtering operation is optimized off-line for each partition cell to achieve the best tradeoff between noise suppression and structure preservation. Recursive filtering operation and recursive weight training are also investigated to further boost the restoration performance. The proposed filter has demonstrated satisfactory results in suppressing many distinct types of noise in natural color images. Noticeable performance gains are demonstrated over other prior-art methods in terms of standard objective measurements, the visual image quality and the computational complexity.     

彩色图像中文本的定位

随着基于内容检索技术的发展，人们逐渐意识到包含在彩色图像和视频中的文本具有重要的语义作用。提取并识别图像中的文本首先需要确定它们的位置。本文提出了一种新的基于连通区域确定彩色图像中文本位置的方法，它首先对图像进行多通道分解以得到连通区域，然后对连通区域的尺寸和位置排列进行分析以确定图像中文本的位置。本文方法不仅能确定水平排列和垂直排列文本的位置，也能确定按一定倾角排列的文本的位置。实验结果表明，该方法可得到较好的文本定位效果。     

基于ICC色彩空间转换的彩色印刷图像数字水印

对现有的数字水印方法应用到彩色印刷图像中存 在水印透明性和鲁棒性差等缺陷, 利用人眼视觉对黄-蓝颜色轴高频变化的敏感度低的特性,提出了基于ICC色彩空间转换 技术的彩色印刷图像数字水印方 法。首先选择与设备无关的CIE L*a*b*颜色空间,在Y-B分 量中嵌入有意义的水印信息;为了抵抗印刷-扫描过程中导致的 图像几何失真,同时避免在同一分量中多次嵌入水印信息导致的图像质量下降,在红- 绿(R-G)分量中嵌入了一个水印同步模 板信号;然后使用调幅加网技术对水印图像进行半色调化处理,使用胶印印刷方式输出;同 时,为了提高水印信号检测的正 确率,在水印检测时,对印刷-扫描图像进行了去网处理。实验结果表明,本文算法对彩 色印刷图像具有很好的水 印透明性,对印刷过程具有较强的鲁棒性,对常规的JPEG压 缩、放大/缩小、旋转等图像处理和几何变换攻击均具 有很强的鲁棒性,可以用于彩色数字图像和印刷图像版权的同步保护。     

一种有效的文档水印技术

针对二值纯文本图像，深入分析二值中文和英文文档图像本身结构特点，并在此基础之上结合人类视觉特性，提出了一种具有一定全局顽健性的局部易碎性数字水印方案。首先将文本图像依据内容进行分块，使每一图像子块只包含一个英文单词或一个字，然后提取该块的可嵌入水印的像素点，最后从中随机选一部分点，嵌入水印信息。实验结果表明该算法在不破坏图像质量基础上，能有效抵抗噪音等攻击，同时又能抵抗和定位对文本内容的局部篡改。     

一种新的图像水印方案

目标区域是图像中视觉上最重要的部分。针对现有的水印算法很少考虑图像中确定的目标区域这一问题，提出了一种基于目标区域的水印方案(WIOR)。方案首先利用小波变换分析图像的目标特征，并依据图像的小波高频系数特征对其进行聚类，获得水印的嵌入域，在此嵌入域中，选择小波系数并对其进行量化调制来嵌入二值扩谱水印；同时，通过只在图像的局部区域内嵌入较少的水印信息来改善水印的隐蔽性。实验结果表明，该方案对于一类具有突出目标特征的图像具有较好的效果。嵌入的水印主要优势在于真正把水印嵌入图像的视觉重要部分，从而能有效地抵御剪切攻击，而且可以实现盲检测。