A robust color image watermarking algorithm against rotation attacks

A robust digital watermarking algorithm is proposed based on quaternion wavelet transform (QWT) and discrete cosine transform (DCT) for copyright protection of color images. The luminance component Y of a host color image in YIQ space is decomposed by QWT, and then the coefficients of four low-frequency subbands are transformed by DCT. An original binary watermark scrambled by Arnold map and iterated sine chaotic system is embedded into the mid-frequency DCT coefficients of the subbands. In order to improve the performance of the proposed algorithm against rotation attacks, a rotation detection scheme is implemented before watermark extracting. The experimental results demonstrate that the proposed watermarking scheme shows strong robustness not only against common image processing attacks but also against arbitrary rotation attacks.     

一种基于HVS和DC分量的DCT域数字水印算法

为增强数字水印的透明性和鲁棒性,提出了一种基于人类视觉系统和直流分量的DCT变换域数字水印算法。算法依据原始图像的纹理掩蔽特性确定水印信息的嵌入位置,依据照度掩蔽特性确定水印信息的嵌入强度,将二值水印图像嵌入到原始图像在DCT域的直流分量中。在仿真实验中与同等条件下的中频嵌入做比较,实验结果表明,该算法提取的水印具有良好的透明性和鲁棒性。     

数字图像版权的水印方案

本文提出了一种新的用于图像数字版权的自适应水印方案,在该方案中,使用混沌映射将商标图像的像素在空间区域中进行随机置乱,然后将置乱的信息埋入在图像的DCT变换域中。为了使水印的分布集中在图像显著的边缘特征中,提出了基于图像像素的模糊熵测度算法,对图像特征系数的修改则是局部自适应的,使得水印埋入的强度随着图像局部变化而变化。嵌入的商标能够在随后的相关检测以及重构中得到很好的恢复以表明数字产品的版权。     

Content Authentication Based on JPEG-to-JPEG Watermarking

A content authentication technique based on JPEG-to-JPEG watermarking is proposed in this paper. In this technique, each 88 block in a JPEG compressed image is first processed by entropy decoding, and then the quantized discrete cosine transform (DCT) is applied to generate DCT coefficients: one DC coefficient and 63 AC coefficients in frequency coefficients. The DCT AC coefficients are used to form zero planes in which the watermark is embedded by a chaotic map. In this way, the watermark information is embedded into JPEG compressed domain, and the output watermarked image is still a JPEG format. The proposed method is especially applicable to content authentication of JPEG image since the quantized coefficients are modified for embedding the watermark and the chaotic system possesses an important property with the high sensitivity on initial values. Experimental results show that the tamper regions are localized accurately when the watermarked JPEG image is maliciously tampered.     

基于Turbo码的DCT域直流分量图像水印算法

文中提出了一种基于Turbo码的DCT变换域直流分量图像水印算法。首先对原始水印信息进行伪随机置乱,接着对置乱的水印进行Turbo编码并进行BPSK调制,生成待嵌入的水印信息。在充分考虑人眼视觉特性的基础上,分别采用两种方式将水印嵌入到DCT变换系数的De分量中,并进行性能比较。丈中对算法在多种常见的攻击如JPEG压缩、噪声、剪切、滤波下进行了仿真。实验结果表明,利用该算法实现的水印具有良好的不可见性和鲁棒性。特别是非自适应加性嵌入方式对JPEG压缩攻击具有很强的鲁棒性。     

Content Authentication Based on JPEG-to-JPEG Watermarking

A content authentication technique based on JPEG-to-JPEG watermarking is proposed in this paper. In this technique, each 8x8 block in a JPEG compressed image is first processed by entropy decoding, and then the quantized discrete cosine transform （DCT） is applied to generate DCT coefficients： one DC coefficient and 63 AC coefficients in frequency coefficients. The DCT AC coefficients are used to form zero planes in which the watermark is embedded by a chaotic map. In this way, the watermark information is embedded into JPEG compressed domain, and the output watermarked image is still a JPEG format. The proposed method is especially applicable to content authentication of JPEG image since the quantized coefficients are modified for embedding the watermark and the chaotic system possesses an important property with the high sensitivity on initial values. Experimental results show that the tamper regions are localized accurately when the watermarked JPEG image is maliciously tampered.     

基于亮度和纹理特征的可见水印技术

数字水印是一种多媒体数字产品版权保护技术。分析了可见水印应具有的特性，提出了基于图像亮度和纹理特征的自适应可见水印方案。采用YUV颜色模型，只对Y分量水印嵌入，以同时适用于彩色或灰度图像。水印嵌入因子是由图像的局部亮度和纹理特征确定，可在满足水印特性的前提下，增加水印嵌入强度，提高水印鲁棒性。试验表明：嵌入水印的图像对中值滤波、有损压缩、加入随机噪声后再滤波等攻击性操作具有较强的鲁棒性，在保持灰度直方图分布基本不变的基础上更加平滑集中，说明水印和原图的统计特性较一致，想在不损坏图像使用质量的前提下，去除或毁坏图像中的可见水印是很困难的。     

Utilizing neighborhood coefficient correlation: a new image watermarking technique robust to singular and hybrid attacks

A new blind digital image watermarking algorithm with watermark embedded in discrete cosine transform (DCT) coefficients is presented in this paper. The proposed scheme exploits correlation between DCT coefficients in neighborhood blocks for embedding. The watermark is embedded by modifying two DCT coefficients, one pertaining to a block in which watermark bit (0 or 1) is to be embedded and the other corresponding to the selected neighborhood block. Both the selected coefficients are modified by a modification factor so that the difference between the pair of coefficients is brought to a predefined zone. This difference between two DCT coefficients is used to extract watermark. The proposed technique has been tested for different attacks like JPEG compression, rotation, cropping, filtering, gaussian noise, salt and pepper noise, histogram equalization etc. It has been observed that the scheme is highly robust not only for the above mentioned attacks used singularly, but also for different possible combinations of simultaneous attacks. A comparison of the proposed technique with some state of art existing algorithms reveals that our scheme provides better results in terms of quality of watermarked images, payload and robustness.     

彩色数字水印嵌入技术

本文提出一种将彩色数字水印嵌入到灰度级图像中的方法.利用静态图像的压缩编码技术,将彩色数字水印编码为一系列二值ID数字,以实现水印的嵌入.由于水印的嵌入过程是基于原始图像的离散余弦变换(DCT)系数之间的关系,所以水印的提取不需要原始图像.实验结果表明本文提出的数字水印技术,经某些图像处理操作和有损压缩后仍是鲁棒的.     

基于DCT变换的彩色图像置乱数字水印算法

介绍了离散余弦变换的系数特征,提出了一种基于离散余弦变换的彩色图像置乱数字水印算法。算法是将数字水印置乱加密后微小的扰动原始彩色图像经离散余弦变换后的对应系数,从而达到数字水印嵌入的目的。仿真实验表明算法简单高效,原图像与嵌入水印后图像差异小,水印提取准确,能较好的保证数字水印不可感知性,在对嵌入水印图像进行各种加噪、裁剪、旋转、锐化等处理后,水印仍有较强的鲁棒性。     

General Architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC Intra Frame Transcoding

The latest international video-coding standard H.264/AVC significantly achieves better coding performance compared to prior video coding standards such as MPEG-2 and H.263, which have been widely used in today’s digital video applications. To provide the interoperability between different coding standards, this paper proposes an efficient architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC intra frame transcoding, using the original information such as discrete cosine transform (DCT) coefficients and coded mode type. Low-frequency components of DCT coefficients and a novel rate distortion cost function are used to select a set of candidate modes for rate distortion optimization (RDO) decision. For H.263 and H.264/AVC, a mode refinement scheme is utilized to eliminate unlikely modes before RDO mode decision, based on coded mode information. The experimental results, conducted on JM12.2 with fast C8MB mode decision, reveal that average 58%, 59% and 60% of computation (re-encoding) time can be saved for MPEG-2, H.263, H.264/AVC to H.264/AVC intra frame transcodings respectively, while preserving good coding performance when compared with complex cascaded pixel domain transcoding (CCPDT); or average 88% (a speed up factor of 8) when compared with CCPDT without considering fast C8MB. The proposed algorithm for H.264/AVC homogeneous transcoding is also compared to the simple cascaded pixel domain transcoding (with original mode reuse). The results of this comparison indicate that the proposed algorithm significantly outperforms the mode reuse algorithm in coding performance, with only slightly higher computation.     

基于小波变换和纹理特征的自适应数字水印的算法

文章提出了一种基于图象纹理特征和DWT变换相结合的自适应数字水印算法，该算法利用了图象本身固有的纹理特征来寻找水印的嵌入位置，实验结果表明这种选择方法可以在降低原始图象视觉失真和经压缩变换后水印图象的失真两方面都达到较好的效果。     

基于改进遗传算法的下采样图像水印算法研究

提出了一种基于遗传算法(GA)的下采样图像盲水印算法.首先对宿主图像下采样,然后用改进的GA全局搜索最优的子图水印嵌入序列,按顺序把符合标准正态分布的水印分量依次嵌入1对子图的离散余弦变换(DCT)系数中.提出的交叉算子和变异算子改进了GA的自适应性和搜索能力,提高了水印算法的综合顽健性.仿真结果表明,该算法添加水印后的图像在保持高保真度的同时,对低通、高通和压缩等攻击的顽健性有明显提升.     

基于正交扩频码和HVS的DCT域图像数字水印技术

文章基于对数字水印通信模型与通信系统相似性的分析,提出了一种利用正交扩频码构造多个独立信道对同一水印进行重复正交嵌入的想法,并引入HVS模型,把图像分块在DCT域分成三类,然后采用不同的嵌入强度系数嵌入到DCT中频系数中,最后从多个独立信道分别提取水印并做合成。实验结果表明,该方案较一般的扩频水印方法对高斯噪声、JPEG压缩、剪切和中值滤波具有更好的鲁棒性。     

在数字图像上实现隐形签名的研究

数字水印作为数字媒体版权保护的有效手段,近几年来在国际上引起了人们极大的兴趣,该文研究了在数字图像上实现隐形签名水印的方法,提出了一个基于小波变换和离散余弦变换(DCT)组合处理的数字图像隐形签名水印方案,它首先对原始图像作适当层次的二维小波分解,然后对低频小波逼近子图和签名水印作二维DCT,最后签名水印的DCT系数被嵌入到逼近子图的中高频段DCT系数中,实验结果表明,所提出的数字图像水印方案很好地实现了图像水印的鲁棒性和不可视性间的统一,经常规的数字图像处理操作及噪声干扰,签名水印仍能被可靠、清晰地检测出。     

Gray-scale image watermarking using GA-BPN hybrid network

In this paper, a novel watermarking scheme is proposed by embedding a binary watermark into gray-scale images using a hybrid GA-BPN intelligent network. HVS characteristics of the images in DCT domain are used to obtain a sequence of weighting factor from a GA-BPN. This weighting factor is used to embed and extract the watermark from the image in DWT domain. The GA-BPN is trained by 27 inference rules that includes three input HVS parameters namely luminance sensitivity, edge sensitivity computed using threshold and contrast sensitivity computed using variance. The robustness of the embedding scheme is examined by executing seven different image processing attacks. Visual quality of signed images before and after the attacks is examined by PSNR. The extracted watermarks from signed and attacked images show a high degree of similarity with the embedded content. Overall, the algorithm is robust against selected attacks and is well optimized.     

结合视频压缩编码的动态图像水印方案

本文提出了一种新的、结合视频压缩编码的动态图像水印方案。在嵌入水印时，充分考虑动态图像压缩编码的特性，对帧内编码帧(I帧)，将水印信息嵌入到DCT低额系数中；面对帧间编码帧(P、B帧)，结合动态补偿/离散余弦变换(MC/DCT)混合编码，把水印信息嵌入到运动补偿后的残差图象的直流成分中。同时，在水印嵌入时，采用扩频技术与多维水印相结合的方法，并通过相关检测的方法判断水印的存在。由于水印的检测是对视频码流直接实施的，不需要对压缩数据进行完全解码，从而大大降低了计算量，提高了视频数据水印的适用性。     

A blind DCT based color watermarking algorithm for embedding multiple watermarks

Multiple watermarking based techniques are receiving more attention in recent times for its wide variety of applications in different fields. To protect the copyright ownership and validate the authenticity of multiple owners, in this paper a color multiple watermarking method based on DCT (Discrete Cosine Transform) and repetition code is proposed and simulated. Initially, green and blue components of color host image are selected for inserting multiple watermarks. Then, each green and blue component of the image is decomposed into non overlapping blocks and subsequently DCT is employed on each block. In this technique, a binary bit of watermark is embedded into green/blue component’s transformed block by modifying some middle significant AC coefficients using repetition code. During multiple watermarks embedding in green and blue components of the proposed method, DC and some higher AC coefficients are kept intact after zigzag scanning of each DCT block to ensure the imperceptibility of the watermarked host image. The proposed scheme is experimented to establish the validity by extracting adequate multiple watermark data from the restructured cover image after applying common geometric transformation attacks (like rotation, cropping, scaling and deletion of lines/columns etc.), common enhancement technique attacks (like lowpass filtering, histogram equalization, sharpening, gamma correction, noise addition etc.) and JPEG compression attacks.     

MPEG-2到H.264转码的快速模式选择算法

研究了MPEG-2到H.264的转码技术,主要偏重帧间和帧内的快速模式选择。提出了基于DCT域SAD的快速帧内模式选择算法以及基于DCT系数阈值的快速帧间模式选择算法。实验表明,在对PSNR和码率影响较小的情况下,本算法能大大提高转码速率。     

MPEG-2到H.264转码中变换系数转换的优化算法

为采用优势明显的H.264编码,并避免已有的大量MPEG-2非线性视频编缉设备被淘汰,研究了从MPEG-2到H.264转码的转换技术,分析了目前的转换算法,提出了一种DCT系数到H.264整数变换(HT)系数转换的优化算法,并针对不同视频终端的应用需求,分别给出了保持图像空间分辨率不变和减半时的转换方法.实验表明,该算法可大幅度简化运算,并具有良好的实时性和视频质量.