高性能全流水线可控参数JPEG-LS编码器实现

提出了一种高性能的JPEG-LS无损/近无损图像压缩算法VLSI实现结构.通过对JPEG-LS算法瓶颈的分析,针对算法中不利于流水线实现的场景缓存部分,采用了一种信号量集机制避免流水线等待.全流水线结构保证了算法实现可以满足高速图像传感器系统的吞吐量需求.同时通过高度参数化的设计,系统可以动态调整和优化算法参数,使压缩效果和效率适应不同的运行环境.算法在FPGA平台通过验证,并得到了接近甚至超过其他A-SIC实现的性能.

面向空间应用的图像压缩技术研究

在空间图像传感器技术向高分辨率、高精度的应用领域迈进的同时，图像数据量的增长向空间飞行器数据存储和传输设备的性能提出了挑战。 为了解决图像质量和系统瓶颈之间的矛盾， 在地面广泛应用的图像压缩技术也在空间领域逐步取得应用。 空间传感图像的关键性和复杂性使得空间图像系统的设计倾向于选择无损或近无损的图像压缩技术。 尽管本文研究的目的是针对特定工程项目进行图像压缩算法的选型和实现，对空间图像压缩技术特点和算法选型策略进行总结也是本文的一项重要任务。JPEG-LS和CCSDS分别是基于预测的编码技术和基于变换的编码技术的典型代表，两者同样支持图像的无损/有损压缩；同样具有较高的压缩率和较低的复杂度；同样便于软硬件实现，并且已经在国内外的空间项目中获得应用。本文对这两种算法原理进行了详细的研究， 并在此基础上对两者的性能和适用环境进行了对比。本文总结了两种算法各自的优点，并提出了对算法局限性的改进方案。 FPGA在图像处理领域一直具有性能方面的优势。近年来随着技术的成熟，FPGA在空间设备中逐渐获得广泛应用。本文对选定的空间图像压缩算法进行了FPGA 实现，并在硬件平台上对算法进行了验证。测试结果表明，本文提出的FPGA实现性能超过国内外其它 FPGA实现，并接近甚至超过部分 ASIC实现。

Improving minimum rate predictors algorithm for compression of volumetric medical images

Medical imaging technologies are experiencing a growth in terms of usage and image resolution, namely in diagnostics systems that require a large set of images, like CT or MRI. Furthermore, legal restrictions impose that these scans must be archived for several years. These facts led to the increase of storage costs in medical image databases and institutions. Thus, a demand for more efficient compression tools, used for archiving and communication, is arising. Currently, the DICOM standard, that makes recommendations for medical communications and imaging compression, recommends lossless encoders such as JPEG, RLE, JPEG-LS and JPEG2000. However, none of these encoders include inter-slice prediction in their algorithms. This dissertation presents the research work on medical image compression, using the MRP encoder. MRP is one of the most efficient lossless image compression algorithm. Several processing techniques are proposed to adapt the input medical images to the encoder characteristics. Two of these techniques, namely changing the alignment of slices for compression and a pixel-wise difference predictor, increased the compression efficiency of MRP, by up to 27.9%. Inter-slice prediction support was also added to MRP, using uni and bi-directional techniques. Also, the pixel-wise difference predictor was added to the algorithm. Overall, the compression efficiency of MRP was improved by 46.1%. Thus, these techniques allow for compression ratio savings of 57.1%, compared to DICOM encoders, and 33.2%, compared to HEVC RExt Random Access. This makes MRP the most efficient of the encoders under study.

St Laurent-lès-Mâcon [le bateau Parisien 2 sur la Saône] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 60536

Features-pooling blind jpeg image steganalysis

In this research, we introduce a new blind steganalysis in detecting grayscale JPEG images. Features-pooling method is employed to extract the steganalytic features and the classification is done by using neural network. Three different steganographic models are tested and classification results are compared to the five state-of-the-art blind steganalysis.

JPEG image steganalysis improvement via image-to-image variation minimization

In this research, we introduce an approach to enhance the discriminative capability of features by employing image-to-image variation minimization. In order to minimize image-to-image variation, we will estimate the cover image from the stego image by decompressing the stego image, transforming the decompressed image and recompressing back. Since the effect of the embedding operation in an image steganography is actually a noise adding process to the image, applying these three processes will smooth out the noise and hence the estimated cover image can be obtained.