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A secure image steganography algorithm based on least significant bit and integer wavelet transform 被引量:4
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作者 ELSHAZLY Emad ABDELWAHAB Safey +3 位作者 ABOUZAID Refaat ZAHRAN Osama ELARABY Sayed ELKORDY Mohamed 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2018年第3期639-649,共11页
The rapid development of data communication in modern era demands secure exchange of information. Steganography is an established method for hiding secret data from an unauthorized access into a cover object in such a... The rapid development of data communication in modern era demands secure exchange of information. Steganography is an established method for hiding secret data from an unauthorized access into a cover object in such a way that it is invisible to human eyes. The cover object can be image, text, audio,or video. This paper proposes a secure steganography algorithm that hides a bitstream of the secret text into the least significant bits(LSBs) of the approximation coefficients of the integer wavelet transform(IWT) of grayscale images as well as each component of color images to form stego-images. The embedding and extracting phases of the proposed steganography algorithms are performed using the MATLAB software. Invisibility, payload capacity, and security in terms of peak signal to noise ratio(PSNR) and robustness are the key challenges to steganography. The statistical distortion between the cover images and the stego-images is measured by using the mean square error(MSE) and the PSNR, while the degree of closeness between them is evaluated using the normalized cross correlation(NCC). The experimental results show that, the proposed algorithms can hide the secret text with a large payload capacity with a high level of security and a higher invisibility. Furthermore, the proposed technique is computationally efficient and better results for both PSNR and NCC are achieved compared with the previous algorithms. 展开更多
关键词 image steganography image processing integer wavelet transform
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Seismic data compression based on integer wavelet transform 被引量:1
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作者 WANG Xi-zhen(王喜珍) TENG Yun-tian(滕云田) +1 位作者 GAO Meng-tan(高孟潭) JIANG Hui(姜慧) 《Acta Seismologica Sinica(English Edition)》 CSCD 2004年第z1期123-128,共6页
Due to the particularity of the seismic data, they must be treated by lossless compression algorithm in some cases. In the paper, based on the integer wavelet transform, the lossless compression algorithm is studied.... Due to the particularity of the seismic data, they must be treated by lossless compression algorithm in some cases. In the paper, based on the integer wavelet transform, the lossless compression algorithm is studied. Comparing with the traditional algorithm, it can better improve the compression rate. CDF (2, n) biorthogonal wavelet family can lead to better compression ratio than other CDF family, SWE and CRF, which is owe to its capability in can- celing data redundancies and focusing data characteristics. CDF (2, n) family is suitable as the wavelet function of the lossless compression seismic data. 展开更多
关键词 lossless compression integer wavelet transform lifting scheme biorthogonal wavelet
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An Approach to Integer Wavelet Transform for Medical Image Compression in PACS
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作者 YANG Yan ZHANG Dong 《Wuhan University Journal of Natural Sciences》 CAS 2000年第2期204-206,共3页
We study an approach to integer wavelet transform for lossless compression of medical image in medical picture archiving and communication system (PACS). By lifting scheme a reversible integer wavelet transform is gen... We study an approach to integer wavelet transform for lossless compression of medical image in medical picture archiving and communication system (PACS). By lifting scheme a reversible integer wavelet transform is generated, which has the similar features with the corresponding biorthogonal wavelet transform. Experimental results of the method based on integer wavelet transform are given to show better performance and great applicable potentiality in medical image compression. 展开更多
关键词 Key words integer wavelet transform lifting scheme lossless compression PACS
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A Recursive High Payload Reversible Data Hiding Using Integer Wavelet and Arnold Transform
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作者 Amishi Mahesh Kapadia P.Nithyanandam 《Intelligent Automation & Soft Computing》 SCIE 2023年第1期537-552,共16页
Reversible data hiding is an information hiding technique that requires the retrieval of the error free cover image after the extraction of the secret image.We suggested a technique in this research that uses a recurs... Reversible data hiding is an information hiding technique that requires the retrieval of the error free cover image after the extraction of the secret image.We suggested a technique in this research that uses a recursive embedding method to increase capacity substantially using the Integer wavelet transform and the Arnold transform.The notion of Integer wavelet transforms is to ensure that all coefficients of the cover images are used during embedding with an increase in payload.By scrambling the cover image,Arnold transform adds security to the information that gets embedded and also allows embedding more information in each iteration.The hybrid combination of Integer wavelet transform and Arnold transform results to build a more efficient and secure system.The proposed method employs a set of keys to ensure that information cannot be decoded by an attacker.The experimental results show that it aids in the development of a more secure storage system and withstand few tampering attacks The suggested technique is tested on many image formats,including medical images.Various performance metrics proves that the retrieved cover image and hidden image are both intact.This System is proven to withstand rotation attack as well. 展开更多
关键词 Reversible data hiding(RDH) integer wavelet transforms(IWT) arnold transform PAYLOAD embedding and extraction
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A COMPRESSION ALGORITHM FOR ECG BASED ON INTEGER LIFTING SCHEME WAVELET TRANSFORM
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作者 Zhang Kunyan Guo Yinjing Lü Wenhong Sun Jinping Wang Xiuzhen 《Journal of Electronics(China)》 2007年第5期674-678,共5页
In view of the shortcomes of conventional ElectroCardioGram (ECG) compression algo- rithms,such as high complexity of operation and distortion of reconstructed signal,a new ECG compression encoding algorithm based on ... In view of the shortcomes of conventional ElectroCardioGram (ECG) compression algo- rithms,such as high complexity of operation and distortion of reconstructed signal,a new ECG compression encoding algorithm based on Set Partitioning In Hierarchical Trees (SPIHT) is brought out after studying the integer lifting scheme wavelet transform in detail.The proposed algorithm modifies zero-tree structure of SPIHT,establishes single dimensional wavelet coefficient tree of ECG signals and enhances the efficiency of SPIHT-encoding by distributing bits rationally,improving zero-tree set and ameliorating classifying method.For this improved algorithm,floating-point com- putation and storage are left out of consideration and it is easy to be implemented by hardware and software.Experimental results prove that the new algorithm has admirable features of low complexity, high speed and good performance in signal reconstruction.High compression ratio is obtained with high signal fidelity as well. 展开更多
关键词 Electro Cardio Gram (ECG) integer lifting scheme wavelet transform Set Partitioning InHierarchical Trees (SPIHT)
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Integer Wavelet-Based Image Interpolation in Lifting Structure for Image Resolution Enhancement
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作者 Chin-Yu Chen Shu-Mei Guo +1 位作者 Ching-Hsuan Tsai Jason Sheng-Hong Tsai 《Applied Mathematics》 2018年第10期1156-1178,共23页
A floating-point wavelet-based and an integer wavelet-based image interpolations in lifting structures and polynomial curve fitting for image resolution enhancement are proposed in this paper. The proposed prediction ... A floating-point wavelet-based and an integer wavelet-based image interpolations in lifting structures and polynomial curve fitting for image resolution enhancement are proposed in this paper. The proposed prediction methods estimate high-frequency wavelet coefficients of the original image based on the available low-frequency wavelet coefficients, so that the original image can be reconstructed by using the proposed prediction method. To further improve the reconstruction performance, we use polynomial curve fitting to build relationships between actual high-frequency wavelet coefficients and estimated high-frequency wavelet coefficients. Results of the proposed prediction algorithm for different wavelet transforms are compared to show the proposed prediction algorithm outperforms other methods. 展开更多
关键词 IMAGE Compression IMAGE Interpolation wavelet transform integer wavelet transform POLYNOMIAL Curve Fitting
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A Novel Zero-Watermark Copyright Authentication Scheme Based on Lifting Wavelet and Harris Corner Detection 被引量:1
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作者 FAN Li GAO Tiegang YANG Qunting 《Wuhan University Journal of Natural Sciences》 CAS 2010年第5期408-414,共7页
In this paper,a novel zero-watermark copyright authentication scheme based on Internet public certification system is proposed.This approach utilizes Haar integer wavelet transform based on a lifting scheme and adapti... In this paper,a novel zero-watermark copyright authentication scheme based on Internet public certification system is proposed.This approach utilizes Haar integer wavelet transform based on a lifting scheme and adaptive Harris corner detection to extract image features,which will be used to produce a binary feature map,and the map is very crucial to the generation of watermark registered later.By properly choosing the parameters of aforementioned techniques such as the threshold T and the radius of local feature region R,the feature map is so much more stable and distinguishing that it can be used to construct robust watermark.Simulations demonstrate that the proposed scheme is resistant to many kinds of signal processing and malicious attacks such as Gaussian blurring,additive noising,JPEG lossy compression,cropping,scaling and slight rotation operation.Compared with a relative scheme such as that of Chang's,the scheme in this paper is more practicable and reliable and can be applied to the area of copyright protection. 展开更多
关键词 zero-watermark copyright authentication Harris corner detection integer wavelet transform ROBUSTNESS
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Second Generation Wavelet Applied to Lossless Compression Coding of Image 被引量:1
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作者 Yan Tang Yu-long Mo 《Advances in Manufacturing》 2000年第3期225-229,共5页
In this paper, the second generation wavelet transform is applied to image lossless coding, according to its characteristic of reversible integer wavelet transform. The second generation wavelet transform can provide ... In this paper, the second generation wavelet transform is applied to image lossless coding, according to its characteristic of reversible integer wavelet transform. The second generation wavelet transform can provide higher compression ratio than Huffman coding while it reconstructs image without loss compared with the first generation wavelet transform. The experimental results show that the se cond generation wavelet transform can obtain excellent performance in medical image compression coding. 展开更多
关键词 wavelet transform integer wavelet image compression lossless coding
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Meaningful image encryption algorithm based on compressive sensing and integer wavelet transform
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作者 Xiaoling HUANG Youxia DONG +1 位作者 Guodong YE Yang SHI 《Frontiers of Computer Science》 SCIE EI CSCD 2023年第3期161-175,共15页
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 algor... 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. 展开更多
关键词 image encryption algorithm compressive sensing integer wavelet transform Hadamard matrix
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Image Watermarking Method Using Integer-to-Integer Wavelet Transforms
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作者 陈韬 王京春 《Tsinghua Science and Technology》 SCIE EI CAS 2002年第5期508-512,共5页
Digital watermarking is an efficient method for copyright protection for text, image, audio, and video data. This paper presents a new image watermarking method based on integer-to-integer wavelet transforms. The wat... Digital watermarking is an efficient method for copyright protection for text, image, audio, and video data. This paper presents a new image watermarking method based on integer-to-integer wavelet transforms. The watermark is embedded in the significant wavelet coefficients by a simple exclusive OR operation. The method avoids complicated computations and high computer memory requirements that are the main drawbacks of common frequency domain based watermarking algorithms. Simulation results show that the embedded watermark is perceptually invisible and robust to various operations, such as low quality joint picture expert group (JPEG) compression, random and Gaussian noises, and smoothing (mean filtering). 展开更多
关键词 digital watermark data hiding STEGANOGRAPHY integer-to-integer wavelet transform
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Medical image lossless compression based on combining an integer wavelet transform with DPCM
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作者 Lihong ZHAO Yanan TIAN +1 位作者 Yonggang SHA Jinghua LI 《Frontiers of Electrical and Electronic Engineering in China》 CSCD 2009年第1期1-4,共4页
To improve the classical lossless compression of low efficiency,a method of image lossless compression with high efficiency is presented.Its theory and the algorithm implementation are introduced.The basic approach of... To improve the classical lossless compression of low efficiency,a method of image lossless compression with high efficiency is presented.Its theory and the algorithm implementation are introduced.The basic approach of medical image lossless compression is then briefly described.After analyzing and implementing differential plus code modulation(DPCM)in lossless compression,a new method of combining an integer wavelet transform with DPCM to compress medical images is discussed.The analysis and simulation results show that this new method is simpler and useful.Moreover,it has high compression ratio in medical image lossless compression. 展开更多
关键词 medical image integer wavelet transform differential plus code modulation(DPCM) lossless compression
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采用IWT和自适应伪Zernike矩的鲁棒可逆水印方案
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作者 高光勇 花锋 +2 位作者 王敏 赵传信 夏志华 《电子学报》 北大核心 2025年第5期1571-1583,共13页
鲁棒可逆水印(Robust Reversible Watermarking,RRW)是近年来信息隐藏领域中一个非常新颖和有价值的研究方向,无论是在图像的版权认证还是高保真领域都有较好发展前景.然而,现有的RRW方案抵抗几何变换、常见攻击以及联合攻击的鲁棒性较... 鲁棒可逆水印(Robust Reversible Watermarking,RRW)是近年来信息隐藏领域中一个非常新颖和有价值的研究方向,无论是在图像的版权认证还是高保真领域都有较好发展前景.然而,现有的RRW方案抵抗几何变换、常见攻击以及联合攻击的鲁棒性较差.为了解决这些问题,本文提出一种采用整数小波变换(Integer Wavelet Transfor⁃mation,IWT)和自适应伪Zernike矩的鲁棒可逆水印方案,该方案在提升水印不可感知性的同时具有可逆性和鲁棒性.首先,由原始图像通过IWT得到低频区域计算生成伪Zernike矩的幅度,然后用自适应归一化方法选择合适的矩,再通过改进的带抖动补偿量化索引调制技术将鲁棒水印嵌入到合适的伪Zernike矩中,对带水印的伪Zernike矩进行重构生成水印图像.最后计算其hash值,并将其与水印图像和原始图像之间的误差、重构误差组成辅助信息嵌入水印图像中,在无攻击的情况下实现载体图像的可逆还原.实验结果表明,本方案对常见信号处理和几何变换攻击具有鲁棒性,相较于近几年提出的RRW方案,本方案在不可见性下实现了更好的鲁棒性. 展开更多
关键词 鲁棒水印 伪ZERNIKE矩 整数小波变换 可逆性 信息隐藏
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基于游程编码和颜色转换的图像安全传输研究
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作者 赵杨宇 姚丙君 +1 位作者 汤震宇 平萍 《计算机仿真》 2025年第5期147-152,220,共7页
由于电力巡检缺陷图像在传输过程中易被攻击者获取和利用,从而对电力公司造成潜在威胁。研究首次结合频域和空域提出了一种基于游程编码和颜色转换的电力巡检缺陷图像安全传输方案。首先,游程编码被首次用于图像隐藏中对缺陷图像进行编... 由于电力巡检缺陷图像在传输过程中易被攻击者获取和利用,从而对电力公司造成潜在威胁。研究首次结合频域和空域提出了一种基于游程编码和颜色转换的电力巡检缺陷图像安全传输方案。首先,游程编码被首次用于图像隐藏中对缺陷图像进行编码,这可降低图像嵌入对掩体图像像素值的损害。然后,在频域下,秘密信息被嵌入到频域的子带中。最后,在空域下,颜色转换被使用以提高含密图像的质量。在模拟实验中,上述方法含密图像的PSNR和MSSIM高于经典的图像隐藏方法,且含密图像能够抵抗残差分析和直方图分析。多方面的实验结果表明该方案在保证缺陷图像无损恢复的前提下显著提高了含密图像的质量,增强了含密图像在不安全网络中传输的安全性。 展开更多
关键词 电力巡检缺陷图像 整数小波变换 游程编码 颜色转换 图像隐藏
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基于整数小波变换的多光谱图像无损压缩 被引量:10
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作者 张荣 俞能海 +1 位作者 刘政凯 吴文忠 《遥感学报》 EI CSCD 北大核心 2001年第1期29-33,共5页
多光谱图像一般都采用预测方法去除空间冗余和谱内冗余实现无损压缩。通过用提升方法构造整数小波变换 ,将变换方法用于去除空间冗余 ;通过分类方法构造谱间预测器 ,用预测方法去除谱间冗余 ,两者相结合 ,实现无损压缩。由于变换方法的... 多光谱图像一般都采用预测方法去除空间冗余和谱内冗余实现无损压缩。通过用提升方法构造整数小波变换 ,将变换方法用于去除空间冗余 ;通过分类方法构造谱间预测器 ,用预测方法去除谱间冗余 ,两者相结合 ,实现无损压缩。由于变换方法的去相关性能良好 ,使该方法压缩效果大大改善。 展开更多
关键词 无损压缩 整数小波变换 多光谱图像 遥感图像 构造谱间预测器
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基于整数小波变换和SVD的视频水印算法 被引量:7
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作者 熊祥光 蒋天发 蒋巍 《计算机工程与应用》 CSCD 2014年第1期78-82,194,共6页
提出了一种以二值图像为水印的混合整数小波变换和奇异值分解的视频水印盲提取算法。对水印图像进行混沌加密和Arnold置乱处理,选择计算复杂度低的直方图算法将视频分割为若干场景;借助密钥随机选取某些场景的亮度分量进行l级整数小波变... 提出了一种以二值图像为水印的混合整数小波变换和奇异值分解的视频水印盲提取算法。对水印图像进行混沌加密和Arnold置乱处理,选择计算复杂度低的直方图算法将视频分割为若干场景;借助密钥随机选取某些场景的亮度分量进行l级整数小波变换,再对低频子带进行分块的奇异值分解;采用量化的方法,将预处理后的水印图像嵌入奇异值分解后的最大奇异值中。在嵌入了水印的视频场景中提取所有的水印版本之后,利用对提取的所有水印信号版本进行统计求和的方法得到最终提取的水印图像。实验表明,提出的算法具有较好的透明性,对常见的处理具有较好的鲁棒性。 展开更多
关键词 视频水印 整数小波变换 奇异值分解 鲁棒性 integer wavelet transform(IWT) Singular Value Decomposition(SVD)
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基于整数小波变换的栅格数字地图数字水印算法 被引量:27
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作者 朱长青 符浩军 +1 位作者 杨成松 王奇胜 《武汉大学学报(信息科学版)》 EI CSCD 北大核心 2009年第5期619-621,625,共4页
根据栅格数字地图亮度高、低频分量变化大、像素值为整数等特点,提出了一种基于整数小波变换的栅格数字地图水印算法。首先将栅格数字地图进行离散整数小波变换,然后分别将水印嵌入到低频分量和高频细节分量。低频分量部分依据其亮度自... 根据栅格数字地图亮度高、低频分量变化大、像素值为整数等特点,提出了一种基于整数小波变换的栅格数字地图水印算法。首先将栅格数字地图进行离散整数小波变换,然后分别将水印嵌入到低频分量和高频细节分量。低频分量部分依据其亮度自适应嵌入周期性扩展水印,细节分量部分根据人类视觉系统特性在感知重要系数中嵌入水印信息。实验表明,该算法对于诸如JPEG压缩、剪裁、锐化、扭曲变形等各种常见的恶意攻击具有良好的鲁棒性。 展开更多
关键词 栅格数字地图 数字水印 整数小波变换
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利用Morlet连续小波变换实现非整次谐波的检测 被引量:71
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作者 薛蕙 杨仁刚 《电网技术》 EI CSCD 北大核心 2002年第12期41-44,共4页
针对常规快速傅立叶变换无法检测非整次谐波的问题,文章提出了利用小波变换实现检测非整次谐波的方法。小波函数是具有时域和频域良好局部化特性的函数,理论上可以用于非整次谐波的检测。但是小波变换存在着由于频谱泄露而带来的混频问... 针对常规快速傅立叶变换无法检测非整次谐波的问题,文章提出了利用小波变换实现检测非整次谐波的方法。小波函数是具有时域和频域良好局部化特性的函数,理论上可以用于非整次谐波的检测。但是小波变换存在着由于频谱泄露而带来的混频问题,给谐波的检测带来误差。为解决此问题,可选择分频严格的小波函数,或者选择合适的分析方法。该文选用的分析方法是连续小波变换,选用的基小波是具有良好频域特性的Morlet小波。通过matlab仿真,在1个周期的采样数据中,能够较为准确地把不同频率的整次和非整次谐波分离出来。这表明了小波变换对于非整次谐波的检测和分析是可行的,从而为谐波的精确检测提供了有效的手段。 展开更多
关键词 连续小波变换 非整次谐波 检测 MORLET小波 电力系统 小波分析
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基于提升框架的整数小波变换 被引量:11
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作者 吴永宏 潘泉 +2 位作者 张洪才 张绍武 张云龙 《电子与信息学报》 EI CSCD 北大核心 2004年第4期659-663,共5页
提升框架可以从一个新的角度来构造小波滤波器,它的核心是确定预测算子和更新算子。该文 引进了多项式局部拟合方法来求取预测算子和更新算子,对每步提升下取整,就实现了整数小波变换.仿真 结果表明,该方法应用于二维数字图像,在一定失... 提升框架可以从一个新的角度来构造小波滤波器,它的核心是确定预测算子和更新算子。该文 引进了多项式局部拟合方法来求取预测算子和更新算子,对每步提升下取整,就实现了整数小波变换.仿真 结果表明,该方法应用于二维数字图像,在一定失真的前提下,具有较高的压缩比,而且小波系数与尺度系 数都是整数,不需要量化步骤.因此,它对于整数数据压缩具有重要的意义. 展开更多
关键词 提升框架 整数小波变换 预测算子 更新算子
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一种适合星上应用的遥感图像有损压缩算法 被引量:16
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作者 田宝凤 徐抒岩 +2 位作者 孙荣春 王昕 闫得杰 《光学精密工程》 EI CAS CSCD 北大核心 2006年第4期725-730,共6页
提出了一种高质量的遥感图像有损压缩算法,在分析了遥感图像经Daubechies双正交小波基D5/3整数小波变换后各子带小波系数统计特性和能量分布的基础上,引入了人类视觉特性,用它来控制算法中的量化方案。根据能量的大小确定不同子带对于... 提出了一种高质量的遥感图像有损压缩算法,在分析了遥感图像经Daubechies双正交小波基D5/3整数小波变换后各子带小波系数统计特性和能量分布的基础上,引入了人类视觉特性,用它来控制算法中的量化方案。根据能量的大小确定不同子带对于目标识别的重要程度,选择不同的量化阈值和量化步长进行量化,并对量化后的数据采用固定比特平面编码。仿真实验表明,该算法对于不同内容和纹理的图像,在一定的压缩比下,均获得了PSNR(峰值信噪比)>30dB的恢复图像,在不损失最低频信息的同时较好地保持了遥感图像中丰富的高频信息,实现了高质量的图像压缩,并且算法简便,快捷,所占用的存储容量小,易于硬件实现,适合于星上应用,减少了在遥感图像压缩中小目标的丢失。 展开更多
关键词 遥感图像 有损压缩 人类视觉 整数小波变换
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一种基于整数小波变换的图像编码算法 被引量:33
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作者 张立保 王珂 《软件学报》 EI CSCD 北大核心 2003年第8期1433-1438,共6页
针对静止图像经整数小波变换(integer wavelet transform)后,各子带系数的幅值动态变化范围小,不利于零树编码(embedded zerotree wavelet coding)的缺点,采用“从1开始的整数平方”代替“2的整数次幂”作为零树编码的量化阈值,缩短了... 针对静止图像经整数小波变换(integer wavelet transform)后,各子带系数的幅值动态变化范围小,不利于零树编码(embedded zerotree wavelet coding)的缺点,采用“从1开始的整数平方”代替“2的整数次幂”作为零树编码的量化阈值,缩短了量化阈值间隔,通过减少重要系数在较低量化阈值中出现的机会,增加了编码过程中的零树数量;同时通过减少参与编码的字符数及对最高频带零树不编码,简化了编码过程。实验结果表明,整数平方量化阈值下的零树编码(integer square zerotree wavelet coding)解决了整数小波变换中零树编码的低效问题,提高了静止图像的编码效率。 展开更多
关键词 整数小波变换 零树编码 整数平方零树编码 2的整数次幂 量化阈值
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