基于JPEG标准的16 bit图像有损压缩应用

给出了16 bit图像有损压缩的原理和详细流程.由于16 bit图像数据量大而JPEG并不支持16 bit图像的压缩,这使得其在存储和传输方面有很多不便.在JPEG压缩方案的基础上,对统计模型进行了扩展(分别对DC差分值编码的统计模型表和AC系数编码的统计模型表进行了一定的改变和扩充),使其能够处理位深度为16的数据,从而实现了16 bit图像的有损压缩.图像量化过程中所使用的量化表是基于JPEG默认的8位亮度图像量化表生成的.所采用的编码器为QM算术编码器,解压后的图像质量评价标准采用客观评价标准PSNR.     

采用超分辨率重建提升压缩图像质量的方法

针对JPEG的中低码率压缩图像即高压缩率图像存在较严重的块效应以及量化噪声,提出了一种对JPEG标准压缩图像进行优化的重建-采样方法.该方法对JPEG压缩图像采用三维块匹配算法(BM3D)进行去噪,去除图像中存在的块效应和量化噪声,进而提高超分辨率重建的映射准确性,再使用外部库对去噪后图像进行基于稀疏表示的超分辨率重建,补充一定的高频信息,最后对重建后的高分辨率图进行双三次下采样,得到与原始图像大小一致的图像作为最终优化图像.实验结果表明,该方法在中低码率情况下能够有效地提高JPEG压缩图像的质量,对高码率压缩图像也有一定效果.     

基于小波和Context模型的海面红外弱小目标检测

红外图像中弱小目标的检测一直是图像处理领域的热点和难点.介绍了一种基于小波变换和Context模型空间自适应滤波的红外弱小目标检测算法.该方法首先利用小波滤波器抑制大部分背景杂波,然后采用基于Context模型的空间自适应滤波器对高频系数做进一步处理,提高信噪比,最后采用基于Bayes分类算法的迭代门限进行图像分割.实验结果表明,与高通滤波相比,该方法能够更有效地检测出弱小目标.     

基于颜色色差的彩色图像压缩技术研究

根据图像DCT变换域系数特征和结合人眼辨别颜色色差的阈值,提出了一种基于颜色色差的彩色图像压缩技术方案。方案首先将彩色图像转化到与设备无关的CIELAB颜色空间,并进行DCT变换和色差计算;再通过人眼辨别颜色色差的阈值进行有选择的量化,并通过Huffman算法进行编码、压缩;最后利用其逆过程进行解压。通过仿真实验,结果表明,重建的彩色解压缩图像与源图像几乎一样,各分量亮度图的解压缩图像的PSNR均超过30dB,人眼几乎不能分辨其差异;衡量编码质量优劣的5个参数值均达到较好效果,且在保证解压缩图像质量的情况下,彩色图像的压缩比能够达到107.167 8,完全可以满足彩色图像压缩的需求。结果表明,提出的基于颜色色差的图像压缩技术方案是一种可行的、较好的彩色图像压缩技术。     

基于M码的地学图形线性四叉树处理方法研究

介绍了基于M码的地学图形数据的线性四叉树编码数据结构，用该数据结构研究了地学图形数据的线性四叉树编码位移、转换、缩放、查找、动态分辨率、地址变换等算法，同时讨论了用C语言实现基于M码的地学图形四叉树编码数据结构的各种算法。该算法适用于地学图形的线性四叉树编码数据的压缩存储和各种逻辑图形操作，可节省大量的存储空间，加快图形／图像数据的运算速度，为计算机图形学的压缩编码技术提供了新的研究手段。     

一种有效的合成孔径雷达原始数据高倍数压缩算法

在分析分块自适应量化(BAQ)压缩数据的分布特性、量化信噪比、动态范围及其对矢量量化数据压缩性能和运算量影响的基础上,对分块自适应矢量量化(BAVQ)压缩算法进行了改进,提出了采用高比特数BAQ压缩的方案.利用改进的BAVQ算法压缩高分辨率SAR原始数据的结果表明,在相同压缩比的条件下,该文提出的改进算法可获得更大的量化信噪比.解压缩数据生成的图像可以清晰地保留图像中的细节信息.     

一种应用于指纹识别系统的指纹图像压缩算法

针对应用于指纹识别系统中指纹图像的压缩编码问题,提出了一种改进的基于四叉树分类的网格编码量化(QTCQ)的指纹图像压缩算法.该算法对小波变换后的高频系数采用2×2的DCT变换进一步集中能量,并对变换后的系数进行系数重排以使得高频子带内的重要系数集中于相应子带的低频位置,再通过基于四叉树的网格编码量化进行量化编码.仿真结果表明,该算法比WSQ和JPEG2000等均具有更好的压缩性能.     

能区分图像或水印篡改的脆弱水印方案

针对现有脆弱型水印方案不能区分是图像内容还是水印被篡改的问题,提出一种能区分图像或水印篡改的脆弱水印方案.该方案用原始图像高7位的小波低频系数非均匀量化后生成的低频压缩图像作为水印,并用混沌系统对水印进行置乱加密,将安全性得到增强的水印直接嵌入到图像的LSB位;认证时通过差值图像定位图像内容被篡改的位置并指出图像中的水印是否被篡改.理论分析和仿真实验表明:该算法不但能精确定位图像内容被篡改的位置,而且能区分是图像内容被篡改、水印被篡改还是两者同时被篡改.     

基于JPEG2000的遥感图像分级量化压缩

介绍了JPEG2000静态图像压缩标准的基本情况;对遥感图像的相关性以及小波变换域统计特性进行了分析,得出遥感图像的特点。针对其特点,设计了基于JPEG2000无损压缩的高频子带分级量化高保真压缩方案。实验结果表明,此方案在对遥感图像进行压缩时取得了较好的效果。     

Multirate 3-D subband coding of video

We propose a full color video compression strategy, based on 3-D subband coding with camera pan compensation, to generate a single embedded bit stream supporting multiple decoder display formats and a wide, finely gradated range of bit rates. An experimental implementation of our algorithm produces a single bit stream, from which suitable subsets are extracted to be compatible with many decoder frame sizes and frame rates and to satisfy transmission bandwidth constraints ranging from several tens of kilobits per second to several megabits per second. Reconstructed video quality from any of these bit stream subsets is often found to exceed that obtained from an MPEG-1 implementation, operated with equivalent bit rate constraints, in both perceptual quality and mean squared error. In addition, when restricted to 2-D, the algorithm produces some of the best results available in still image compression.     

Wavelet compression of ECG signals by the set partitioning in hierarchical trees algorithm

A wavelet electrocardiogram (ECG) data codec based on the set partitioning in hierarchical trees (SPIHT) compression algorithm is proposed in this paper. The SPIHT algorithm [1] has achieved notable success in still image coding. We modified the algorithm for the one-dimensional case and applied it to compression of ECG data. Experiments on selected records from the MIT-BIH arrhythmia database revealed that the proposed codec is significantly more efficient in compression and in computation than previously proposed ECG compression schemes. The coder also attains exact bit rate control and generates a bit stream progressive in quality or rate.     

一种基于混沌和密钥交换的流加密算法

传统的流加密算法,存在密钥分发和管理以及加密强度不高两大难题。利用混沌及密钥交换的思想,提出了一种新颖的流加密算法。该算法首先由密钥交换得到混沌初始值,再由混沌映射和明文进行有机结合,生成密钥流,然后与明文进行按位异或运算,得到密文。由于混沌加密能够有效的提高加密强度,同时密钥交换可以很好的解决密钥分发和管理的难题。因此,该算法能够改善传统流加密算法中存在的两大难题。     

Image coding based on wavelet transform and uniform scalar dead zone quantizer

In this paper, a new wavelet transform image coding algorithm is presented. The discrete wavelet transform (DWT) is applied to the original image. The DWT coefficients are firstly quantized with a uniform scalar dead zone quantizer. Then the quantized coefficients are decomposed into four symbol streams: a binary significance map symbol stream, a binary sign stream, a position of the most significant bit (PMSB) symbol stream and a residual bit stream. An adaptive arithmetic coder with different context models is employed for the entropy coding of these symbol streams. Experimental results show that the compression performance of the proposed coding algorithm is competitive to other wavelet-based image coding algorithms reported in the literature.     

Context- and HVS-Based Multiwavelet Image Coding Using SPIHT Framework

In this paper, multiwavelets are considered in the context of image compression based on the human vision system (HVS). First, selecting the BSA (4/4)* filters, a twodimensional image is transformed with our proposed algorithm I. Second, we apply HVS coefficients into the subbands of the transformed image. Third, we split the coefficients into two parts: the significance map and residue map. Then a new modified set partitioning in hierarchical trees (SPIHT) algorithm is proposed to encode the significance map. Fourth, algorithm III is presented for coding the residue map. Finally, we adopt context-based adaptive arithmetic coding to encode the bit stream. We also provide some experimental results proving that multiwavelets are worth studying and compare them with those of other multiwavelet and JPEG2000 algorithms.     

一种基于对象几何形状的视频抗误码方法

针对压缩视频流中的误码,提出了一种新颖的基于对象几何形状的视频抗误码方法.首先,在编码端通过比较帧间编码帧内邻近宏块的运动向量差异获得粗略的对象几何形状信息,以对象标示图表示;再把它以与标准码流兼容的方式嵌入到压缩码流里去;最后,在解码端利用它帮助精确的构造错误宏块的运动向量.试验结果表明,该方法对于即使大量连续slice出错的情况仍能获得比较好的掩盖效果,而增加的运算复杂度和传输负载量都不大.     

Embedded image coding using zerotrees of wavelet coefficients

The embedded zerotree wavelet algorithm (EZW) is a simple, yet remarkably effective, image compression algorithm, having the property that the bits in the bit stream are generated in order of importance, yielding a fully embedded code. The embedded code represents a sequence of binary decisions that distinguish an image from the “null” image. Using an embedded coding algorithm, an encoder can terminate the encoding at any point thereby allowing a target rate or target distortion metric to be met exactly. Also, given a bit stream, the decoder can cease decoding at any point in the bit stream and still produce exactly the same image that would have been encoded at the bit rate corresponding to the truncated bit stream. In addition to producing a fully embedded bit stream, the EZW consistently produces compression results that are competitive with virtually all known compression algorithms on standard test images. Yet this performance is achieved with a technique that requires absolutely no training, no pre-stored tables or codebooks, and requires no prior knowledge of the image source. The EZW algorithm is based on four key concepts: (1) a discrete wavelet transform or hierarchical subband decomposition, (2) prediction of the absence of significant information across scales by exploiting the self-similarity inherent in images, (3) entropy-coded successive-approximation quantization, and (4) universal lossless data compression which is achieved via adaptive arithmetic coding     

高斯脉冲串在光纤中运行时的热折射噪声分析

当高斯脉冲串在光纤中运行时,脉冲功率耗散使光纤温度上升,引起光纤折射率变化,结果产生热折射噪声.在利用光孤子存储环探测引力红移时,热折射噪声会影响光孤子的运行时间,这种影响可以由研究高斯脉冲串给出.在光纤一维热传导方程的基础上,计算出了光纤温度涨落的上限,并确定了脉冲串总运行时间的上限跟脉冲串比特率的关系.通过该关系,人们可以根据运行时间的变化和测量装置灵敏度的要求来选择合适的脉冲串的比特率,从而对设计使用光孤子存储环之类的脉冲串的装置提供帮助,为光孤子存储环探测引力红移提供参考依据.     

基于改进的K-L变换的多光谱图像压缩算法

融合离散小波变换(DWT,discrete wavelet tran sform)与Karhunen-Loeve变换(KLT),将图像的能量集中到少数系数上,以达到更好的 压缩效果。首先将多光谱图像的每个谱段进行快速9/72D DWT,消除多光谱图像的大部分 空间冗余;然后对所有谱段产生的小波系数进行改进的KLT,来消除光谱冗余和残存的空 间冗余;最后对所得谱段产生的小波系数进行改进的KLT,来消除光谱冗余和残存的空间冗 余;最后对所得系数进行熵编码,得到压缩码流。实验结果表明,在码率为0.25～2.0bit/ pixel范围内,平均信噪比(SNR)高于41dB,同时缩短了运 算时间,从而提升了多光谱图像压 缩算法的性能。     

Bit level image encryption algorithm based on hyperchaotic system

Because chaotic systems are unpredictable, ergodic and sensitive to initial values and parameters, they are often used in the field of encryption. To avoid the bad randomness of the random key generated by the low dimensional chaotic map system, a 5-dimensional multi-wing hyperchaotic system is adopted in this paper. The key stream generated by the chaotic system is related to the plaintext image. So it can effectively resist the attacks of selecting plaintext. The plaintext graph is decomposed into binary form by bit plane decomposition technique, and then these bit planes are divided into high and low groups. The designed control matrix is used to identify the specific scrambling mode, and each bit is permuted within and between groups. Finally, bit diffusion is used to change the pixel value of each pixel. Theoretical analysis and numerical simulation show that the algorithm has good encryption performance for image encryption.