Accelerating BPC-PaCo through Visually Lossless Techniques

Fast image codecs are a current need in applications that deal with large amounts of images. Graphics Processing Units (GPUs) are suitable processors to speed up most kinds of algorithms, especially when they allow fine-grain parallelism. Bitplane Coding with Parallel Coefficient processing (BPC-PaCo) is a recently proposed algorithm for the core stage of wavelet-based image codecs tailored for the highly parallel architectures of GPUs. This algorithm provides complexity scalability to allow faster execution at the expense of coding efficiency. Its main drawback is that the speedup and loss in image quality is controlled only roughly, resulting in visible distortion at low and medium rates. This paper addresses this issue by integrating techniques of visually lossless coding into BPC-PaCo. The resulting method minimizes the visual distortion introduced in the compressed file, obtaining higher-quality images to a human observer. Experimental results also indicate 12% speedups with respect to BPC-PaCo.     

JPEG encryption for image rescaling in the encrypted domain

This work proposes a novel protocol of encrypting the JPEG image suitable for image rescaling in the encrypted domain. To protect the privacy of original content, the image owner perturbs the texture and randomizes the structure of the JPEG image by enciphering the quantized Discrete Cosine Transform (DCT) coefficients. After receiving the encrypted JPEG image, the service provider generates a rescaled JPEG image by down-sampling the encrypted DCT coefficients. On the recipient side, the encrypted JPEG image rescaled by the service provider can be decrypted to a plaintext image with a lower resolution with the aid of encryption keys. Experimental results show that the proposed method has a good capability of rescaling the privacy-protected JPEG file.     

一种基于ADV212图像压缩的方法

高效的硬件图像压缩系统可以有效的减少图像数据的冗余度,在分析专用编解码芯片ADV212的基础上,设计了一种现场可编程门阵列(FPGA)组合ADV212的图像压缩系统,实现对720×288的静态图像进行JPEG2000压缩.FPGA用来实现时序控制和数据转换,ADV212则进行图像的压缩.本次实验主要是改变图像压缩倍数及小波变换级数,并采用峰值信噪比(peak signal to noise ratio,PSNR)和均方误差(mean squared error,MSE)两个参数来衡量压缩图像的质量.实验结果表明,该系统可实现图像的有效压缩,并且压缩倍数越大图像失真越严重,小波变换级数在3级以上时图像质量较好.     

A chaotic-cipher-based packet body encryption algorithm for JPEG2000 images

A chaotic-cipher-based packet body encryption algorithm for JPEG2000 images is proposed in this paper. In order to produce a compliant codestream, a 2-byte block encryption procedure including bit-wise exclusive OR and cyclic rotation operations is investigated. Moreover, a repeatedly encryption process is adopted to eliminate the undesirable marker codes during encryption. The repeatedly encryption process only introduces a negligible computational overhead. Both simulations and analysis show that the proposed algorithm is of high security and simplicity. Therefore, these good properties make the algorithm efficient to process and useful for image applications.     

基于小波变换的硬拷贝全息水印

提出一种基于离散小波变换的硬拷贝数字全息水印方法。首先利用共轭对称延拓傅里叶计算全息生成水印全息图;然后对其进行小波分解,将包含全部水印信息的高频分量嵌入到载体图像小波分解的中频区域以实现信息隐藏。由于全息图的频谱可控性和不可撕毁性,本文全息水印方法具有很好的不可见性,可以实现水印盲提取,不仅能够抵抗剪切、噪声、滤波和...     

基于OpenMP的JPEG2000并行解码算法的实现

为了提高JPEG2000的解码速度,在多核处理器平台上利用OpenMP（Open specifications for Multi Processing）实现了JPEG2000的高速并行解码。即利用OpenMP对JPEG2000解码过程中的T1解码器和离散小波逆变换进行多路并行解码,减少了这两部分的运行时间,从而降低JPEG2000的整体解码时间。实验结果表明,OpenMP是一种简单而有效的并行化编程工具,在保证解码图像质量不变的前提下,相对单线程串行算法,所提出的并行解码算法,解码速度有显著提高。     

基于JPEG双量化特性的彩色伪造图像盲检测

现有的盲检测方法主要针对灰度图像和未压缩图像,很多算法都不能有效地检测彩色压缩伪造图像.本文提出了一种利用JPEG双量化失真特性实现彩色压缩伪造图像旨检测的方法.通过分析伪造图像的制作过程,可知由多幅JPEG图像拼接成的高质量彩色伪造图像中篡改区域和背景区域经历的双量化过程不同.根据这一特性,本文首先使用背景区域的初始量化表估计值对待检测图像进行再压缩处理,定义再压缩后图像各颜色分量的失真函数;然后根据各失真函数在图像不同区域的取值,由各颜色分量分别确定篡改区域;最后综合彩色图像各颜色分量的检测结果,最终识别出彩色图像篡改区域的位置和大小.仿真结果表明该方法不但可以有效地识别彩色伪造图像的篡改区域,而且比基于单一颜色分量的检测方法更加准确.     

基于ARM9的无线视频监控系统的设计

采用ARM9微处理器为核心,设计了基于ARM9的无线视频监控系统。通过嵌入式Linux系统采集到USB摄像头的视频数据,将其经过JPEG编码压缩;在ARM9控制下,采集到的数据通过无线发送／接受模块,进行视频数据传输发送到接收端,再将视频数据通过RS232／RJ45网络接口提交给监控PC;再由视频应用服务端将接收到的压缩数据帧重组并复合,从而实现无线视频监控。系统结构简单、性能可靠,具有广泛应用前景。     

JPEG算法的研究及其在医学图像中的应用

图像压缩编码的目的就是要用尽量少的比特数表示图像,同时保持复原图像的质量,使它符合特定应用场合的要求。在介绍经典压缩算法中有代表性的编码算法的同时,重点介绍了JPEG基本算法;研究了JPEG算法的基本原理,分模块分析研究了DCT变换、量化、熵编码和游程编码的原理和功能,并且采用MATLAB程序设计语言对JPEG算法进行仿真实现,得到了较好质量的压缩图像。     

An effective approach for wavelet lifting based on filter optimization and median operator

In JPEG2000, the Cohen–Daubechies–Feauveau (CDF) 9/7‐tap wavelet filter implemented by using the conventional lifting scheme has two problems. The first problem is that the filter coefficients are remaining complex; second, the conventional lifting scheme ignores image edges in the coding process. In this article, we propose an effective wavelet lifting scheme to solve these problems. For this purpose, we design the optimal 9/7‐tap wavelet filters in two steps. In the first step, we select the appropriate filter coefficients; in the second step, we employ a median operator to consider image edges. Experimental results from using the median lifting scheme and combining filter optimization and median lifting show that our proposed methods outperform the well‐known CDF 9/7‐tap wavelet filter of JPEG2000 on edge‐dominant images. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 359–366, 2010