基于2D-FFT的掌静脉图像Gabor滤波快速增强法

手掌静脉纹识别技术作为新一代高精度的生物特征识别技术,被广泛用于个人身份鉴定领域.有效提取手掌静脉特征对于手掌静脉分类至关重要.然而,由于采集到的手掌静脉图像的质量较差,必须在识别前对手掌静脉图像进行增强.使用二维离散快速傅里叶变换（2D-FFT）代替传统空域卷积滤波,实现Gabor滤波器与原图像的频域卷积滤波.实验结果显示,本文提出的增强方法,相比较传统的自适应直方图均衡化和Retinex算法具有更佳的增强效果,相比于传统Gabor空域卷积滤波具有更低的计算复杂度,更适用于实时系统.     

一种新的基于Hough变换的椭圆轮廓检测方法

Hough变换是一种检测曲线的有效方法,但使用传统的Hough变换来检测椭圆计算量过大。为此提出了一种新的基于Hough变换的椭圆轮廓检测方法,该方法利用椭圆中心是平面上所有点中距离椭圆轮廓上点最大距离最小的点这一几何性质,降低了Hough参数空间的维度,从而有效地降低了计算量。使用该方法可以快速地判断一个输入图形的轮廓是否为椭圆。     

基于Hough变换的图象检测对偶点法

提出了图形边界对偶点的概念,证明了对对称图形对偶点的存在性及其关于平移、缩放和旋转组合变换的不变性;结合Hough变换,建立了一种快速的图象检测方法,详细给出圆和椭圆检测的对偶点算法,并补充了文献[1]中公式的不足,实验结果表明,该对偶点法除保留了Hough变换法的容错性和鲁棒性外,还具有很快的计算速度,而且可以灵活地应用于解决一些较难的图象检测问题。     

基于归一化灰度Hough变换的SAR图像舰船尾迹检测算法

舰船尾迹检测作为近年来SAR图像海洋应用的一个重要方面而受到关注。目前大多数研究都是利用Radon变换作为数学工具，结果得到增强的是尾迹特征，而不是尾迹的端点。从提取尾迹的端点坐标出发，在传统Hough变换算法基础上进行改进，提出了基于归一化灰度Hough变换的SAR图像舰船尾迹检测算法，并推导出尾迹端点反演算法，同时自动提取舰船的航速，取得了较好的实验结果。     

A Fast Hough Transform for the Parametrisation of Straight Lines using Fourier Methods

The Hough transform is a useful technique in the detection of straight lines and curves in an image. Due to the mathematical similarity of the Hough transform and the forward Radon transform, the Hough transform can be computed using the Radon transform which, in turn, can be evaluated using the central slice theorem. This involves a two-dimensional Fourier transform, an x-y to r-θ mapping and a 1D Fourier transform. This can be implemented in specialized hardware to take advantage of the computational savings of the fast Fourier transform. In this paper, we outline a fast and efficient method for the computation of the Hough transform using Fourier methods. The maxima points generated in the Radon space, corresponding to the parametrisation of straight lines, can be enhanced with a post transform convolutional filter. This can be applied as a 1D filtering operation on the resampled data whilst in the Fourier space, so further speeding the computation. Additionally, any edge enhancement or smoothing operations on the input function can be combined into the filter and applied as a net filter function.     

Recovering 3D motion of multiple objects using adaptive Houghtransform

We present a method to determine 3D motion and structure of multiple objects from two perspective views, using adaptive Hough transform. In our method, segmentation is determined based on a 3D rigidity constraint. Instead of searching candidate solutions over the entire five-dimensional translation and rotation parameter space, we only examine the two-dimensional translation space. We divide the input image into overlapping patches, and, for each sample of the translation space, we compute the rotation parameters of patches using least-squares fit. Every patch votes for a sample in the five-dimensional parameter space. For a patch containing multiple motions, we use a redescending M-estimator to compute rotation parameters of a dominant motion within the patch. To reduce computational and storage burdens of standard multidimensional Hough transform, we use adaptive Hough transform to iteratively refine the relevant parameter space in a “coarse-to-fine” fashion. Our method can robustly recover 3D motion parameters, reject outliers of the flow estimates, and deal with multiple moving objects present in the scene. Applications of the proposed method to both synthetic and real image sequences are demonstrated with promising results     

六角形阵快速傅立叶变换波束形成算法

在六角形阵阵元数较多时,传统的频域相移求和波束形成方法要求的运算量很大.为此提出一种采用六角形快速傅立叶变换HFFT(Hexagonal Fast Fourier Transform)的波束形成算法.使用六角形傅立叶变换HDFT(Hexagonal Discrete Fourier Transform)完成六角形阵的波束形成,由于HDFT存在快速算法HFFT,因此能够显著降低波束形成的运算量.首先在各个通道上做FFT,将信号变换到频域,然后转角重排,再对各个阵元上相同的频点做HFFT,得到频域常规波束形成输出.理论分析表明,对于窄带信号的六角形阵波束形成,所提出的算法所需的计算量比传统的相移求和方法降低了95%以上.仿真和试验结果表明,提出的算法在不影响阵列处理性能的同时,显著降低了波束形成所需的计算量,易于工程实现.     

图像配准中图像互信息的快速估计算法

快速、精确地估计图像互信息是图像配准中一个非常重要的课题,它涉及到两幅图像的联合概率密度和边缘概率密度的估计。针对核密度估计法运算量大而导致互信息估计速度慢的问题,提出了一种快速核密度估计法,并用它估计图像互信息。快速算法利用了单位冲激函数性质和基于快速傅立叶变换的快速卷积算法,能在线性时间复杂度内估计互信息。采用临床MRI图像的实验证实了快速算法的性能。     

On the inverse Hough transform

In this paper, an inverse Hough transform algorithm is proposed. This algorithm reconstructs correctly the original image, using only the data of the Hough transform space and it is applicable to any binary image. As a first application, the inverse Hough transform algorithm is used for straight-line detection and filtering. The lines are detected not just as continuous straight lines, which is the case of the standard Hough transform, but as they really appear in the original image, i.e., pixel by pixel. To avoid the quantization effects in the Hough transform space, inversion conditions are defined, which are associated only with the dimensions of the images. Experimental results indicate that the inverse Hough transform algorithm is robust and accurate     

The Partial Fast Fourier Transform

An efficient algorithm for computing the one-dimensional partial fast Fourier transform \(f_j=\sum _{k=0}^{c(j)}e^{2\pi ijk/N} F_k\) is presented. Naive computation of the partial fast Fourier transform requires \({\mathcal O}(N^2)\) arithmetic operations for input data of length N. Unlike the standard fast Fourier transform, the partial fast Fourier transform imposes on the frequency variable k a cutoff function c(j) that depends on the space variable j; this prevents one from directly applying standard FFT algorithms. It is shown that the space–frequency domain can be partitioned into rectangular and trapezoidal subdomains over which efficient algorithms can be developed. As in the previous work of Ying and Fomel (Multiscale Model Simul 8(1):110–124, 2009), the contribution from rectangular regions can be reduced to a series of fractional-phase Fourier transforms over squares, each of which can be reduced to a convolution. In this work, we demonstrate that the partial Fourier transform over trapezoidal domains can also be reduced to a convolution. Since the computational complexity of a dealiased convolution of N inputs is \({\mathcal O}(N\log N)\), a fast algorithm for the partial Fourier transform is achieved, with a lower overall coefficient than obtained by Ying and Fomel.     

一种快速霍夫变换算法

霍夫变换是图像处理中的一种常用的检测算法，能够有效地在较大的噪声环境中提取图像中的特定信息。但标准的霍夫变换算法运算量大，处理速度慢，有较大的局限性。该文讨论了一种快速霍夫变换算法，该算法有效地降低了传统霍夫变换算法的时间复杂度，提高了计算效率和运算速度，对于提高图像处理的速度，增强图像处理的实时性有着显著的作用。     

水下人造目标线特征快速检测算法

为了从水下复杂场景中快速检测人造目标,提出了一种在图像小波变换低频子带上进行直线实时检测的算法。首先,利用小波变换确定显著线特征检测的合适尺度;然后在确定的低频子带小图像上进行边缘检测,利用梯度直方图和迭代法相结合自适应确定边缘检测的分割阈值,得到显著特征的边缘点;再利用改进的Hough变换检测人造目标的直线特征;最后在原始图像上标记出直线检测的结果。实验结果表明:提出的算法可以准确检测出水下复杂背景中人造目标的直线特征,并且具有良好的实时性,满足水下人造目标视频检测的应用要求。     

A fast digital Radon transform—An efficient means for evaluating the Hough transform

A fast digital Radon transform based on recursively defined digital straight lines is described, which has the sequential complexity of N² log N additions for an N × N image. This transform can be used to evaluate the Hough transform to detect straight lines in a digital image. Whilst a parallel implementation of the Hough transform algorithm is difficult because of global memory access requirements, the fast digital Radon transform is vectorizable and therefore well suited for parallel computation. The structure of the fast algorithm is shown to be quite similar to the FFT algorithm for decimation in frequency. It is demonstrated that even for sequential computation the fast Radon transform is an attractive alternative to the classical Hough transform algorithm.     

Generalized Hough Transform Using Regions with Homogeneous Color

A novel generalized Hough transform algorithm which makes use of the color similarity between homogeneous segments as the voting criterion is proposed in this paper. The input of the algorithm is some regions with homogeneous color. These regions are obtained by first pre-segmenting the image using the morphological watershed algorithm and then refining the resultant outputs by a region merging algorithm. Region pairs belonging to the object are selected to generate entries of the reference table for the Hough transform. Every R-table entry stores a relative color between the selected region pairs. This is done in order to compute the color similarity and in turn generate votes during the voting process and some relevant information to recover the transformation parameters of the object. Based on the experimental results, our algorithm is robust to change of illumination, occlusion and distortion of the segmentation output. It recognizes objects which were translated, rotated, scaled and even located in a complex environment.     

基于MSER-Otsu与直线矫正的仪表指针定位算法

针对配电站无人值守作业机器人执行巡检任务时对指针式仪表的识读需求,提出一种结合MSER-Otsu阈值分割与Hough变换直线矫正的仪表指针定位算法。利用最大稳定极值区域算法从表盘图像中粗提取出指针区域,引入迭代Otsu算法进一步对该区域进行阈值分割,将指针、阴影和背景区域像素点分离后仅保留指针的二值化图像,对其采用Hough变换进行指针中心线预定位,再以Huber loss为最优化函数对预定位直线进行矫正,最终完成指针中心线的定位。实验结果表明,该算法能在复杂环境中对仪表指针进行精确定位并计算指针偏转角度,与Hough变换算法和Huber loss拟合算法等相比,其处理速度更快且鲁棒性更高,能满足配电站巡检机器人的实际需求。     

形状角计算改进及其在矩形目标识别中的应用

目的 在轮廓特征识别中,形状角理论已经被证明为一种有效方法.形状角的计算精度和时间开销取决于轮廓上各离散点处切线方向的计算效率.现有基于Vialard算法的切线方向计算方法在处理矩形轮廓时步骤烦琐且存在较大的误差,导致使用形状角识别矩形时效率不高.针对此问题,提出一种基于傅里叶拟合的离散点切线方向计算方法.方法 首先对离散点进行极坐标转化,然后使用傅里叶级数拟合整个轮廓,最后再对拟合之后的曲线求导,从而计算出轮廓上各点的切线方向.结果 在本文所给出的实例中,本文方法计算平均耗时为1.5775 s,传统方法平均耗时为156.155 s,且计算结果更加精确.结论 本文方法可以避免Vialard算法及其衍生方法在处理矩形轮廓时产生的过度迭代的问题,时间复杂度降低两个数量级,结果更加准确.最后,将所提的改进形状角计算方法应用矩形轮廓识别中,通过实例分析,验证了该方法的准确性和可靠性.     

Performance of dual tone multi-frequency signal decoding algorithm using the sub-band non-uniform discrete Fourier transform on the ADSP-2192 processor

Efficient decoding of Dual Tone Multi-Frequency (DTMF) signals can be achieved using the sub-band non-uniform discrete Fourier transform (SB-NDFT). In this paper, the details of its implementation on the ADSP-2192 processor are put forward. The decoder performance in terms of its computational complexity and computational speed of this algorithm, implemented on the ADSP-2192 processor, are compared for different implementations of the SB-NDFT algorithm, with and without optimization for the chosen DSP, ADSP-2912. The algorithm is tested for various types of input signals on the DSP and these are compared with the results from Matlab^®. Problems on using other DTMF decoding algorithms that use the conventional discrete Fourier transform (DFT) and the non-uniform discrete Fourier transform (NDFT) are also addressed.     

采用人工鱼群的改进广义Hough变换目标定位

目的：传统广义Hough变换可以在平移、旋转、缩放、局部遮挡等情况下,对任意目标进行定位,但是存在定位速度较慢、存储空间较大、累加器空间离散化等缺点。方法：因此提出了基于全局自适应人工鱼群的广义Hough变换算法,对目标进行更快地定位。根据目标形状的极坐标信息建立精简R表,去除梯度信息,降低计算复杂度,同时提高目标模型的鲁棒性。然后,根据精简R表计算待测目标模型函数值,作为人工鱼的适应度值,人工鱼群采用自适应的感知范围和步长,通过不断交互并协调行为,在连续的多维累加器空间中启发式地搜索最优目标模型参数,从而标定出目标的准确位置。结果：实验结果表明,该算法只需要常量级的存储空间开销,并且与广义Hough变换算法相比速度提高了90%以上,较大地减少了空间和时间开销,也提高了目标的定位精度。结论：本文提出了一种新的累加器空间搜索策略,能够更快速准确地定位目标,特别是在复杂背景下对复杂目标定位更为明显。     

Hough变换在表面污渍检测中的应用

针对具体芯片图像的形状特征,提出了基于改进Hough变换的几何配准算法.该算法利用边缘点的梯度方向信息,以及通过圆上任意一点并沿着该点法线方向的直线必定经过该圆的圆心这一几何性质,将三维Hough变换空间简化为二维空间,较好地解决了传统广义Hough变换运算时间长、存储空间大的问题.实验表明,可以有效地对两幅图像进行配准,从而检测出芯片表面的污渍.     

Hough变换在中文名片图像倾斜校正中的应用

近来,文档图像的计算机自动理解已取得很多进展。但是,对于具有倾斜的图像的理解仍然存在许多困难。这种困难在中文名片图像自动识别与理解系统中尤为突出。必须在系统的输入端对图像作有效的倾斜校正以保证系统的性能。由于中文名片版面复杂,名片中文字行以及每行字符较少,使得现有的倾斜校正算法在处理名片图像时效果很不理想。Hough变换可用于一般文档图像的倾斜校正。但是,Hough变换在名片图像中的应用还有待研究。本文提出一种二级Hough变换算法,并应用于名片图像理解系统,利用名片图像自身的特点提高Hough变换的精确度和速度。这一方法的效果已被实验结果所证实。