基于DA算法的二维DCT的FPGA实现

研究了一种采用现场可编程门阵列(FPGA)实现超高性能二维离散余弦变换(DCT)的方法。在DCT算法结构上利用了变换的可分离性和行列的可分解性采用行列分解的方法将二维DCT转换为2个串行的一维DCT实现,同时采用了基于分布算法(Distributed Arithmetic)的乘法累加结构,从而极大地减少了硬件资源需求,提高了运算速度,使图像处理的实时性得到了大幅提高。最后还给出了FPGA的实现和仿真结果。     

基于DSP Bulider二维DCT实现

图像DCT(离散余弦变换)是图像压缩的一项重要技术,如何准确、快速地进行图像压缩一直是国内外研究的热点.首先阐述DCT算法原理以及适合硬件设计的快速算法,介绍DSP Builder信号处理平台,重点研究基于DSP Builder平台的2D-DCT硬件实现.在二维DCT时,采用一种存取数据时直接对数据转置的方法,以提高设计速度.然后在Model-sim 6.2平台下进行功能仿真.最后将DSP Builder模块转换成VHDL语言,并在Quartus RⅡ下进行编译和时序仿真,达到了理想的效果.     

基于NEDA算法的二维DCT硬件加速器的设计实现

应用二维DCT的图像压缩系统,DCT的运算量较大,为了突破该瓶颈,设计了基于NEDA算法的DCT硬件加速器,该设计方案采用移位相加代替乘法运算,并用RAM代替ROM,有效地节省了硬件资源.给出了Verilog仿真结果,结果表明该加速器可以在使用资源非常少的情况下,正确地实现二维DCT运算,适合于各种视频图像压缩方面的应用.     

基于DCT变换的图像压缩技术研究

图像DCT变换是图像压缩的一项重要技术，如何准确、快速的进行图像压缩一直是国内外研究的热点。概要的论述了图像DCT变换的概念和特点，对基于DCT变换的图像压缩技术的算法进行了研究，并用MATLAB进行了算法仿真，取得了较为理想的效果。     

基于DCT图像压缩过程的分析与研究

利用离散余弦变换(DCT)对图像进行分块压缩,即对每个方块执行二维离散余弦变换,将变换得到的量化DCT系数进行编码和传送,形成压缩后的图像格式。在接收端,将量化的DCT系数进行解码,并对每个8×8方块进行二维IDCT,最后将操纵完成的方块组合成一幅完整的图像。实验主要利用了DCT域能量具有方向性的特点,通过计算机仿真实验,表明量化值的选取对图像压缩有明显的影响,因此,要根据图像质量来决定量化值的大小。     

图像压缩编码中Walsh变换与DCT变换及其比较

图像变换是图像处理的基础,是图像压缩的第一步。在图像压缩中,DCT变换因其变换效果好而被广泛采用,成为目前最常用的图像压缩变换方法,而Walsh变换还未被广泛采用。通过对这两种变换的算法分析以及Matlab仿真实验和峰值信噪比的对比,结果表明,walsh变换在算法上比DCT简单,实现较为容易,其变换性能并不亚于DCT变换,在某些量化级上甚至还优于DCT变换,Walsh变换有着广泛的应用前景。     

DCT变换域的数字水印技术研究

分析了一维和二维DCT变换的原理,分析了DCT变换域的数字水印技术中DCT变换系数的选择依据,重点研究了DCT变换域的数字水印嵌入与提取方法,并且利用VC++进行编程验证,实验测试表明,基于DCT变换域的数字水印技术具有较好的实用性。     

基于小波变换的图像压缩编码研究综述

图像压缩是指以尽量少的比特数代表原来图像的技术.小波变换由于在时域和频域同时具有局域化特性,弥补了DCT变换的不足,其多分辨率特性还便于与人眼视觉特性相结合.小波图像编码还便于与其它新兴图像编码方法相结合,成为当前研究热点.文中介绍了小波变换的基本理论,讨论了小波图像压缩研究现状和进展,并指出存在的主要问题,最后展望小波图像压缩编码的发展前景.     

基于TMS320CDSC21的MPEG4编码器二维DCT变换的实现

首先介绍了二维DCT变换算法,然后描述了实现该算法的TI公司的TMS320CDSC21芯片的结构特点.最后给出了一种程序编写简单、结构清晰、执行效率高的实现二维DCT变换的设计方法.     

基于二维DCT的图像压缩编码及其实现

DCT变换是图像压缩的一项重要技术,如何准确、快速进行图像压缩一直是国内外研究的热点。主要介绍基于DCT变换的图像压缩编码算法,给出具体的实现方法和步骤,并用Matlab进行了算法仿真。实验结果表明,该算法实现简单,在很大压缩范围内,都能得到很好的重建图像质量,满足不同场合要求不同图像质量的实际需要。这里利用Matlab做仿真实验,方法简单、速度快且误差小,大大提高了图像压缩的效率和精度。     

Logo extraction using dynamic stochastic resonance

This paper presents a novel technique for watermark (logo) extraction from the distorted watermarked images. The proposed technique is based on the combined discrete wavelet transform (DWT), discrete cosine transform (DCT), and dynamic stochastic resonance (DSR). In this technique, DCT transform is applied to the DWT coefficients of the watermarked image. Later on, variance is calculated from the DCT coefficients, and it is used to tune the DCT coefficient with the help of dynamic double-well system parameters that causes resonance to DCT coefficients. The experimental results have been compared with the existing techniques and were found superior in terms of peak-value-of-signal-to-noise-ratio (PSNR) and correlation coefficient.     

Block-based frequency scalable technique for efficient hierarchical coding

In this paper, we propose a block-based frequency scalable technique for efficient hierarchical coding. The proposed technique divides an image into its multiple resolution versions, based on the spectral properties of discrete cosine transform (DCT) kernels. We present that spectral decomposition, downsampling, and DCT operations are performed effectively over input DCT coefficients of one-dimensional (1-D) and two-dimensional (2-D) signals by using the proposed transform matrices. The proposed image coder is observed to reduce the computational complexity and the memory buffer size with a higher peak signal-to-noise ratio (PSNR), when compared with the traditional hierarchical image coder. In addition, the proposed architecture can preserve compatibility easily with the previous DCT-based image coder.     

一种用于实时视频处理的高速二维DCT的电路设计和实现

绝大多数的国际图像和视频压缩标准都采用DCT(离散余弦变换)进行传输编码。本文介绍了一种基于矩阵分解算法的高速实时二维DCT处理器。为了满足视频处理的实时性，整个电路设计中广泛采用了流水线技术，文中详细介绍了二维DCT处理器的电路结构，最后给出了它的FPGA实现。     

Facial Feature Extraction Based on Private Energy Map in DCT Domain

This letter presents a new feature extraction method based on the private energy map (PEM) technique to utilize the energy characteristics of a facial image. Compared with a non‐facial image, a facial image shows large energy congestion in special regions of discrete cosine transform (DCT) coefficients. The PEM is generated by energy probability of the DCT coefficients of facial images. In experiments, higher face recognition performance figures of 100% for the ORL database and 98.8% for the ETRI database have been achieved.     

Separation of image parts using 2-D parallel form recursive filters

This correspondence deals with a new technique to separate objects or image parts in a composite image. A parallel form extension of a 2-D Steiglitz-McBride method is applied to the discrete cosine transform (DCT) of the image containing the objects that are to be separated. The obtained parallel form is the sum of several filters or systems, where the impulse response of each filter corresponds to the DCT of one object in the original image. Preliminary results on an image with two objects show that the algorithm works well, even in the case where one object occludes another as well as in the case of moderate noise.     

Utilizing neighborhood coefficient correlation: a new image watermarking technique robust to singular and hybrid attacks

A new blind digital image watermarking algorithm with watermark embedded in discrete cosine transform (DCT) coefficients is presented in this paper. The proposed scheme exploits correlation between DCT coefficients in neighborhood blocks for embedding. The watermark is embedded by modifying two DCT coefficients, one pertaining to a block in which watermark bit (0 or 1) is to be embedded and the other corresponding to the selected neighborhood block. Both the selected coefficients are modified by a modification factor so that the difference between the pair of coefficients is brought to a predefined zone. This difference between two DCT coefficients is used to extract watermark. The proposed technique has been tested for different attacks like JPEG compression, rotation, cropping, filtering, gaussian noise, salt and pepper noise, histogram equalization etc. It has been observed that the scheme is highly robust not only for the above mentioned attacks used singularly, but also for different possible combinations of simultaneous attacks. A comparison of the proposed technique with some state of art existing algorithms reveals that our scheme provides better results in terms of quality of watermarked images, payload and robustness.     

基于DCT变换的QWT域改进的图像盲水印算法

针对数字图像的版权保护,基于离散余弦变换和四元数小波变换,提出了一种新的改进的盲水印算法,先根据待嵌入水印的大小对载体图像进行四元数小波变换,获得与幅值和相位信息相对应的4幅低频子带,然后对每个低频子带分别进行全局离散余弦变换,最后通过修改两个随机子带中特定位置上DCT系数的大小关系嵌入水印,利用分阶线性Logistic映射产生的混沌序列预处理经Arnold置乱后的水印信息和确定水印的嵌入位置.实验结果表明,该算法对添加噪声、JPEG压缩、滤波和亮度及对比度调整等攻击都具有很强的鲁棒性.     

图像边缘信息的谱分析及其在变换编码中的应用

本文对边缘信息的ＤＣＴ频谱特征做了分析。通过理论推导及事例分析证得含平直单边缘图像子块，其ＤＣＴ变换系数能量并不总是集中分布在与其空间边缘走向垂直的方向上。将研究结果应用于变换编码的分类环节，提出一种按边缘信息的频谱特性分类的方法。实验结果表明了该方法的有效性。