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二维离散小波变换计算量较大,并要求相当大的缓存空间,使JPEG2000在星载图像压缩和小型便携式设备中的应用受到限制。基于行的小波变换能降低对存储容量的要求,后拉伸变换的提升算法能减少离散小波变换的乘法运算量。为此,提出了一种基于行的快速提升算法,该算法将行列运算操作结合起来进行,以累进方式完成列向小波的提升步计算,节省了内存;并且充分利用了后拉伸变换的优点,减少了乘法运算量。 相似文献
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基于纹理的自适应提升小波变换图像压缩 总被引:4,自引:0,他引:4
经典二维小波变换仅在图像的水平和竖直方向应用小波滤波,不能提供灵活的方向信息,对纹理信息丰富的自然图像稀疏化效果不理想,在基于小波变换的图像压缩中还需改进.为了实现更有效的图像的稀疏表示,文中提出一种新型的基于图像纹理的自适应提升小波变换:根据局部特征将图像自适应分块,预先判断局部图像纹理方向,保持正交性质不变;沿纹理方向应用小波滤波,结合提升变换格式实现即位运算;沿纹理方向插值获取分数像素值,保护纹理信息不被破坏,总体变换对图像纹理描述更有效;结合JPEG2000中的编码方法EBCOT,对变换系数和方向信息分别编码,应用于图像压缩.仿真实验是在数值结果和视觉效果上将文中方法和JPEG2000方法作比较,以体现文中方法的优越性. 相似文献
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根据提升小波的框架结构,提出了一种基于JEPG2000的二维多级提升小波变换核的FPGA设计。 采用分时复用和流水结构,充分利用FPGA片内存储资源,实现了行列变换的并行执行。在保证精度的前提下采用优化的移位加操作代替浮点乘运算,加快了运算速率,减小了电路规模。同时通过乒乓操作完成FPGA和片外SDRAM间数据的无缝缓冲处理,保证了多级变换的高效实时并行,从而达到各级小波系数的快速并行输出。系统经验证完全满足图像实时处理的要求,为后续实时压缩编码和传输提供了有利条件。 相似文献
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图象数据压缩是当前研究的热点之一.本文针对现在流行的JPEG 2000标准和提升小波算法进行分析.首先介绍了第一代和第二代小波变换以及整数小波变换,并就JPEG 2000对两种小波压缩方法实验效果和效率进行比较,从实验结果可知,Daubechies 9/7小波压缩效果最好. 相似文献
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基于提升小波变换的感兴趣区域编码技术是静态图像压缩标准JPEG2000支持的一种非常重要的功能,本文提出了一种对医学图像病灶(感兴趣)区域采用5/3提升小波变换,对图像背景(非感兴趣)区域采用9/7提升小波变换的方法,该方法与传统JPEG2000采用单一提升小波变换对医学进行压缩后的效果相比较,具有更高的压缩性能. 相似文献
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JPEG2000压缩算法研究 总被引:4,自引:4,他引:0
由于JPEG2000采用零树编码方式实现压缩,编码过程中零树的形成个数与压缩效率CE密切相关;对小波滤波器及JPEG2000零树熵编码进行研究,发现高的小波变换层数和5/3滤波器的使用有利于增加零树个数,从而提高压缩率;实现基于拼接块小波变换的JPEG2000压缩算法,结果显示图像分成拼接块会影响编码效率和解码保真度;对JPEG和JPEG2000进行比较,得出在超低码率下,JPEG2000解码图像虽然没有采用JPEG时出现的“方块”效应,但有“飞萤”效应。 相似文献
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基于提升的小波变换算法,提出了一种有效的JPEG2000小波变换的VLSI实现结构。采用了时分复用技术优化结构设计,实现了数据变换的细节分量和近似分量交替输出,以及有效减少了所用乘法器、加法器运算单元和寄存器单元数量,从而有效减少系统占用面积和功耗。该结构实现简单、规则,具有很好的扩展性,非常适合于VLSI设计实现。 相似文献
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基于整数小波变换的图像压缩算法 总被引:1,自引:0,他引:1
IWT(integer wavelet transform)是一种基于提升格式整数小波变换的图像压缩算法.IWT比传统的浮点小波变换效率要高.在硬件实现时,整数运算比浮点运算便宜,基于提升格式的整数分解时所需的存储空间只是传统变换的一半.基于此考虑有损压缩,图像先作基于提升格式的整数分解,然后结合改进的EZW和自适应量程编码.在编码性能不受影响的情况下,此算法比Shaprio的EZW编码要快1.5倍. 相似文献
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首先提出了基于提升方案的形状自适应整数小波变换算法。然后对整数小波同第一代小波的变换系数分布特性的差异进行了详细的分析.针对整数小波变换系数幅值动态变化范围小,而传统EZW中阈值区间相对较大,不利于形成零树结构的不足,提出了基于奇数平方的阈值选取方法.并在此基础上,提出一种基于二分法的量化逼近方案,与传统的基于住平面的量化方法相比,该方案能用更少的比特来完全重构一个系数.最后,提出了基于整数小波变换和新的量化方案的形状自适应EZW编码算法.实验结果表明,闽值选取方法是合理的,而基于二分法的量化逼近方案是有效的.在相同码率下,与传统阈值选取和量化方案相比,该方法重构图像的峰值信噪比要高出0.5~2dB. 相似文献
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为了提高提升格式下整数小波变换的有损压缩性能,提出了基于最佳补偿比例因子的优化算法。根据变换后小波系数和滤波器的特性,分别采用子带近似线性逼近和量化补偿噪声取代取整运算的方法,求得小波分解后各个子带的最佳补偿比例因子。利用这个比例因子补偿整数小波变换的非线性带来的近似误差以达到优化目的。实验结果表明,在不增加运算复杂度的情况下,所得压缩图像的峰值信噪比(PSNR)与基于浮点运算的传统离散小波变换几乎一样。 相似文献
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A motion compensated lifting (MCLIFT) framework for the 3D wavelet video coding is proposed in this paper. By using bi-directional motion compensation in each lifting step of the temporal direction, the video frames are effectively de-correlated. With the proper entropy coding and bit-stream packaging schemes, the MCLIFT wavelet video coder is scalable at frame rate and quality level. Experimental results show that the MCLIFT video coder outperforms the 3D wavelet video coder without motion by an average of 0.9-1.3dB, and outperforms MPEG-4 coder by an average of 0.2-0.6dB. 相似文献
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In order to get a characterized wavelet with expected properties, a new wavelet is constructed by using the lifting scheme
(LS). Taking the low-pass filter of cubic B-splines wavelet transform as an initial filter, and designing a lifting operator
based on interpolating subdivision method, new wavelet is obtained through one lifting step. The wavelet inherits the property
of low-pass filtering that the initial filter possessed, and also has ability to extract transient impulse from analyzed signal.
By making an equivalent interchange manipulation to the LS framework, and removing decimators, a LS algorithm for undecimated
wavelet transform (UWT) is proposed. Two engineering applications are reported in the paper, and the results show that the
UWT can provide much more diagnostics information than the classical wavelet transform. 相似文献
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A new meaningful image encryption algorithm based on compressive sensing (CS) and integer wavelet transformation (IWT) is proposed in this study. First of all, the initial values of chaotic system are encrypted by RSA algorithm, and then they are open as public keys. To make the chaotic sequence more random, a mathematical model is constructed to improve the random performance. Then, the plain image is compressed and encrypted to obtain the secret image. Secondly, the secret image is inserted with numbers zero to extend its size same to the plain image. After applying IWT to the carrier image and discrete wavelet transformation (DWT) to the inserted image, the secret image is embedded into the carrier image. Finally, a meaningful carrier image embedded with secret plain image can be obtained by inverse IWT. Here, the measurement matrix is built by both chaotic system and Hadamard matrix, which not only retains the characteristics of Hadamard matrix, but also has the property of control and synchronization of chaotic system. Especially, information entropy of the plain image is employed to produce the initial conditions of chaotic system. As a result, the proposed algorithm can resist known-plaintext attack (KPA) and chosen-plaintext attack (CPA). By the help of asymmetric cipher algorithm RSA, no extra transmission is needed in the communication. Experimental simulations show that the normalized correlation (NC) values between the host image and the cipher image are high. That is to say, the proposed encryption algorithm is imperceptible and has good hiding effect. 相似文献
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针对目前大多数图像水印技术是关于灰度图像并且基于离散小波变换的研究,提出了一种基于整型小波变换(Integer Wavelet Transform,IWT)将彩色数字水印嵌入到彩色宿主图像中的算法。采用YCbCr色彩空间的Y分量嵌入水印,利用人类视觉系统特性(Human Visual System,HVS)实现彩色水印嵌入位置的自适应确定;彩色水印的提取不需要原始水印和原始宿主图像。实验证明,嵌入水印后的图像具有很好的不易觉察性,并且对常见的图像处理操作具有很强的鲁棒性。 相似文献
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提出了一种自适应提升小波变换算法,该算法是根据待分析信号的局部特点,自适应的选择更新器,自适应更新器的选择,主要是保持图像边缘不被平滑,防止出现大的小波系数。为确保系统的稳定性,又提出了采用先更新后预测的提升结构。在此结构中,预测过程不影响更新过程,这也为自适应算法的重构提供了有利条件,由于稳定性高、高频系数小以及能够完全重构,使得此方法有利于压缩性能的提高。通过实验证明了该算法的有效性。 相似文献
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In this paper, a new robust and secure digital image watermarking scheme that can be used for copyright protection is proposed. The scheme uses the integer wavelet transform (IWT) and singular value decomposition (SVD). The grey image watermark pixels values are embedded directly into the singular values of the 1-level IWT decomposed sub-bands. Experimental results demonstrate the effectiveness of the proposed scheme in terms of robustness, imperceptibility and capacity due to the IWT and SVD properties. A challenge due to the false positive problem which may be faced by most of SVD-based watermarking schemes has been solved in this work by adopting a digital signature into the watermarked image. The proposed digital signature mechanism is applied to generate and embed a digital signature after embedding the watermarks; the ownership is then authenticated before extracting watermarks. Thus, the proposed scheme achieved the security issue where the false positive problem is solved, in addition to that, the scheme is considered as a blind scheme. A computer simulation is used to verify the feasibility of the proposed scheme and its robustness against various types of attacks and to compare it with some previous schemes. Furthermore, the statistical Wilcoxon signed rank test is employed to certify the effectiveness of the proposed scheme. 相似文献