基于DCT系数大小关系的自适应JPEG隐写

JPEG图像是最流行的隐写载体之一,但隐写分析的最新进展表明,如何设计安全的JPEG隐写算法仍是一个困难的问题.本文提出了一种新的JPEG自适应隐写方法.自适应隐写难点在于设计失真函数合理反应修改量化DCT系数造成的嵌入失真.由于量化DCT系数绝对值的大小能够反应JPEG图像主要统计特性,本文根据DCT系数大小关系设计失真函数,结合STC（Syndrome Trellis Codes）编码,分别给出了使用nsF5修改方式的单层嵌入方法以及使用加减一修改方式的双层嵌入方法.实验表明,本文单层嵌入方法比nsF5安全性高,双层嵌入方法比nsF5以及Filler’s Method抵抗多种检测的能力更强.     

JPEG图像压缩对测量类图像的影响

在JPEG图像压缩的量化过程中,丢弃了部分高频信息,使图像的清晰度下降。通过对频谱的对照分析和对实际图像进行实验后表明,JPEG图像压缩对测量和处理结果的影响与原图像的特点、取样方式、滤波过程和压缩算法有关。经摄像机和图像卡获得的图像,其压缩比可达到10;经扫描仪获得的图像,其压缩比可达到6;经数码相机获得的图像,其压缩比可达到6～8;对特定的医学图像、晶相图像等来说,利用图像的特征构造最优匹配的JPEG压缩量化表,其压缩比可达到10。采用合适的压缩比和改进的压缩方法,图像的细节损失可以控制在较小的范围内,基本上不影响检测类图像的边界提取、分割、尺寸测量时的处理结果。     

一种采用JPEG标准的实时视频图像压缩处理系统

本文重点探讨了在设计ＪＰＥＧ视频压缩应用系统时，应着重考虑的几个重要技术问题，并介绍了一种采用以ＰＣ为平台，以ＣＬ５５０视频压缩处理器和８２Ｃ９００１视频窗口控制器为基础的实时视频图像压缩处理系统。描述了该系统总体构成，深入讨论了图像数据缓冲存储和压缩速率控制等关键技术问题。     

Compression Helps Deep Learning in Image Classification

The impact of JPEG compression on deep learning (DL) in image classification is revisited. Given an underlying deep neural network (DNN) pre-trained with pristine ImageNet images, it is demonstrated that, if, for any original image, one can select, among its many JPEG compressed versions including its original version, a suitable version as an input to the underlying DNN, then the classification accuracy of the underlying DNN can be improved significantly while the size in bits of the selected input is, on average, reduced dramatically in comparison with the original image. This is in contrast to the conventional understanding that JPEG compression generally degrades the classification accuracy of DL. Specifically, for each original image, consider its 10 JPEG compressed versions with their quality factor (QF) values from {100,90,80,70,60,50,40,30,20,10}. Under the assumption that the ground truth label of the original image is known at the time of selecting an input, but unknown to the underlying DNN, we present a selector called Highest Rank Selector (HRS). It is shown that HRS is optimal in the sense of achieving the highest Top k accuracy on any set of images for any k among all possible selectors. When the underlying DNN is Inception V3 or ResNet-50 V2, HRS improves, on average, the Top 1 classification accuracy and Top 5 classification accuracy on the whole ImageNet validation dataset by 5.6% and 1.9%, respectively, while reducing the input size in bits dramatically—the compression ratio (CR) between the size of the original images and the size of the selected input images by HRS is 8 for the whole ImageNet validation dataset. When the ground truth label of the original image is unknown at the time of selection, we further propose a new convolutional neural network (CNN) topology which is based on the underlying DNN and takes the original image and its 10 JPEG compressed versions as 11 parallel inputs. It is demonstrated that the proposed new CNN topology, even when partially trained, can consistently improve the Top 1 accuracy of Inception V3 and ResNet-50 V2 by approximately 0.4% and the Top 5 accuracy of Inception V3 and ResNet-50 V2 by 0.32% and 0.2%, respectively. Other selectors without the knowledge of the ground truth label of the original image are also presented. They maintain the Top 1 accuracy, the Top 5 accuracy, or the Top 1 and Top 5 accuracy of the underlying DNN, while achieving CRs of 8.8, 3.3, and 3.1, respectively.     

用于JPEG2000图像认证的鲁棒性水印算法

针对JPEG2000图像压缩标准所具有的渐进传输、一次编码多次解码等特性,提出了一种基于图像特征的鲁棒性图像认证算法.该算法在JPEG2000编码过程中,先根据图像不变特征,生成认证水印,再根据实际的鲁棒性认证需求,在量化后的小波系数中确定每个子带的认证水印嵌入位平面,最后基于小波系数位平面的特征嵌入认证水印.算法不仅能适应JPEG2000各种灵活的编码方式,还能定位图像篡改的位置.实验结果验证了图像认证算法对可允许图像操作的鲁棒性以及对图像篡改的敏感性.     

有损压缩JPEG在载频条纹图分析中的应用研究

探讨了基于JPEG的有损压缩方法在载频条纹图分析中的应用前景。简介了当今流行的JPEG有损压缩技术和傅里叶变换轮廓术。使用专业软件对傅里叶变换轮廓术中拍摄的载频条纹图进行各种压缩比的压缩,解压后再解调出相位,与未经压缩的原图解调出的相位进行比较。将其相位误差与相位移法解调出的相位误差进行了对比,指出相对于相位移法而言,傅里叶变换轮廓术具有滤波的作用,对其拍摄的载频条纹图,应用JPEG压缩算法是可能的,解调出来的相位误差更小。     

Benchmarking JPEG 2000 implementations on modern CPU and GPU architectures

The use of graphics hardware for non-graphics applications has become popular among many scientific programmers and researchers as we have observed a higher rate of theoretical performance increase than the CPUs in recent years. However, performance gains may be easily lost in the context of a specific parallel application due to various both hardware and software factors. JPEG 2000 is a complex standard for data compression and coding, that provides many advanced capabilities demanded by more specialized applications. There are several JPEG 2000 implementations that utilize emerging parallel architectures with the built-in support for parallelism at different levels. Unfortunately, many available implementations are only optimized for a certain parallel architecture or they do not take advantage of recent capabilities provided by modern hardware and low level APIs. Thus, the main aim of this paper is to present a comprehensive real performance analysis of JPEG 2000. It consists of a chain of data and compute intensive tasks that can be treated as good examples of software benchmarks for modern parallel hardware architectures. In this paper we compare achieved performance results of various JPEG 2000 implementations executed on selected architectures for different data sets to identify possible bottlenecks. We discuss also best practices and advices for parallel software development to help users to evaluate in advance and then select appropriate solutions to accelerate the execution of their applications.     

编码系统研究及VLSI实现

提出了一种JPEG2000编码系统结构和VLSI方案.该方案以小波子带为单位,多套并行处理.对JPEG2000标准中各个模块的算法进行了逻辑化简、并行编码等优化.如采用双行并行9/7提升小波分解,条带并行的比特平面编码,简化区间更新和并行归一化算术编码等.各模块均以流水线方式工作,其中的比特平面编码和算术编码采用异步流水线方式动态分配执行时间,加速比均接近于流水段数3.以图像信号产生板送入原始图像,编码后送入PC机进行码流截断和解压缩.该系统在各个压缩率下的信噪比与LuraWave商用压缩软件的差距均在0.8 dB之内,可见改进后的算法可行且有效,像元时钟可达20 MHz.     

Chaotic encryption and decryption of JPEG image

According to encrypting principles of digital images, integrating the characteristic of JPEG image, and using discrete chaotic sequence, this paper has studied encryption and decryption of JPEG image, and has compared and analyzed the corresponding relations between the encryption and decryption effects and their security of two different encrypting schemes of the JPEG image chaotic encryption studied by this paper. In a basic unit of an 8 × 8 data block, image encryption and decryption not only are fast, but also match with JPEG format. The JPEG image encryption can meet the security requirement of the storage and transmission of JPEG images in some common application occasions, and provides an effective and feasible way of encrypting JPEG images.     

基于JPEG2000的压缩图像纹理信息重建

提出了基于JPEG2000的压缩图像纹理信息重建的一种方法．该方法在编码端用高斯模型来描述图像的统计纹理信息，并对这些纹理信息进行统计和编码，在解码端根据编码的信息重建图像的纹理．通过和非线性量化扩展补偿法的结果在客观指标和主观品质上的比较，说明本文提出的方法可以通过较小的比特开销（低于10％）重建丢失的纹理信息，从而获取压缩图像的品质在主观视觉效果上的提高．