An Improved Method for Edge Detection and Image Segmentation Using Fuzzy Cellular Automata

Image segmentation is one of the most important and challenging problems in image processing. The main purpose of image segmentation is to partition an image into a set of disjoint regions with uniform attributes. In this study, we propose an improved method for edge detection and image segmentation using fuzzy cellular automata. In the first stage, we introduce a new edge detection method based on fuzzy cellular automata, called the texture histogram, and empirically demonstrate the efficiency of the proposed method and its robustness in denoising images. In the second stage, we propose an edge detection algorithm by considering the mean values of the edges matrix. In this algorithm, we use four fuzzy rules instead of 32 fuzzy rules reported earlier in the literature. In the third and final stage, we use the local edge in the edge detection stage to more accurately accomplish image segmentation. We demonstrate that the proposed method produces better output images in comparison with the separate segmentation and edge detection methods studied in the literature. In addition, we show that the method proposed in this study is more flexible and efficient when noise is added to an image.     

Edge and line feature extraction based on covariance models

Image segmentation based on contour extraction usually involves three stages of image operations: feature extraction, edge detection and edge linking. This paper is devoted to the first stage: a method to design feature extractors used to detect edges from noisy and/or blurred images. The method relies on a model that describes the existence of image discontinuities (e.g. edges) in terms of covariance functions. The feature extractor transforms the input image into a “log-likelihood ratio” image. Such an image is a good starting point of the edge detection stage since it represents a balanced trade-off between signal-to-noise ratio and the ability to resolve detailed structures. For 1-D signals, the performance of the edge detector based on this feature extractor is quantitatively assessed by the so called “average risk measure”. The results are compared with the performances of 1-D edge detectors known from literature. Generalizations to 2-D operators are given. Applications on real world images are presented showing the capability of the covariance model to build edge and line feature extractors. Finally it is shown that the covariance model can be coupled to a MRF-model of edge configurations so as to arrive at a maximum a posteriori estimate of the edges or lines in the image     

Edge Detection in Range Images Based on Scan Line Approximation

In this paper we present a novel edge detection algorithm for range images based on a scan line approximation technique. Compared to the known methods in the literature, our algorithm has a number of advantages. It provides edge strength measures that have a straightforward geometric interpretation and supports a classification of edge points into several subtypes. We give a definition of optimal edge detectors and compare our algorithm to this theoretical model. We have carried out extensive tests using real range images acquired by four range scanners with quite different characteristics. Using a simple contour closure technique, we show that our edge detection method is able to achieve a complete range image segmentation into regions. This edge-based segmentation approach turns out to be superior to many region-based methods with regard to both segmentation quality and computational efficiency. The good results that were achieved demonstrate the practical usefulness of our edge detection algorithm.     

Edge detection: a review of dissimilarity evaluations and a proposed normalized measure

In digital images, edges characterize object boundaries, so edge detection remains a crucial stage in numerous applications. To achieve this task, many edge detectors have been designed, producing different results, with various qualities of segmentation. Indeed, optimizing the response obtained by these detectors has become a crucial issue, and effective contour assessment assists performance evaluation. In this paper, several referenced-based boundary detection evaluations are detailed, pointing out their advantages and disadvantages, theoretically and through concrete examples of image edges. Then, a new normalized supervised edge map quality measure is proposed, comparing a ground truth contour image, the candidate contour image and their associated spatial nearness. The effectiveness of the proposed distance measure is demonstrated theoretically and through several experiments, comparing the results with the methods detailed in the state-of-the-art. In summary, compared to other boundary detection assessments, this new method proved to be a more reliable edge map quality measure.     

改进的小波变换在中医舌象边缘检测中的研究

针对目前常见的边缘检测算法对噪声较为敏感,获取的边缘不够精细,且容易出现伪边缘或边缘重叠等情况,结合中医舌象的特点,在小波变换边缘检测算法的基础上提出了改进的小波变换边缘检测算法。该算法通过对图像每一行、列的边缘信息逐位算出相邻位差,并在位差的差值变化大小之间检测小波极值。实验结果证明,该方法能有效解决传统边缘检测算法对去除噪声和获取精细边缘之间的矛盾,使边缘重叠现象大为减少,从而获得了比较理想的边缘检测效果,为以后整个舌体区域的分割提取打下了良好的基础。     

基于边缘约束局部区域MRF的图像分割方法

针对常规马尔科夫随机场（MRF）模型对复杂自然图像分割时,存在对噪声敏感且边缘模糊的问题,构建一种基于边缘约束局部区域MRF（ECLRMRF）的图像分割模型。利用欧氏距离度量局部区域内邻接像素的相似度,依据其相似度构建局部空间来约束高斯混合模型,有效描述丰富的局部区域统计特征,并建立MRF模型的局部区域一致性约束项。利用Canny边缘检测算子提取图像的边缘特征,并在分割过程中建立图像分割区域的边缘约束,通过在MRF模型框架下将局部区域统计特征和图像边缘特征相融合,解决局部区域MRF模型对图像分割边缘模糊的问题,再采用Gibbs采样算法实现对复杂自然图像的准确分割。实验结果表明,该模型能够更好地保留图像边缘信息,并且具有更好的分割效果。     

基于局部直方图相关的造影图象边缘检测方法

造影图象的边缘检测是造影图象的组织或器官分割、测量和分析的基础 .由于造影图象的信噪比低、低电平纹理多 ,而且大量边缘是渐变的小幅度微弱边缘 ,因而其检测一直是造影图象研究与临床应用的重点之一 .针对这一问题 ,提出了一种检测数字造影图象边缘的新方法 .由于图象边缘区域与非边缘区域的局部直方图明显不同 ,因而可以利用这种差别来检测图象的边缘 ,同时还基于局部直方图构造了一种匹配滤波器算法——最大统计相关算法 ,该方法不敏感于图象的噪声和低电平纹理 ,而且能够有效地从噪声和纹理中分离提取造影图象的微弱边缘 .     

结合分水岭的纹理梯度各向异性图像分割

目的 目前,许多图像分割算法对含有丰富纹理信息的图像的分割效果并不理想,尤其是在不同纹理的边缘信息的保持方面。为了解决这一问题,提出一种基于连续纹理梯度信息的各向异性图像分割算法。方法 在分水岭算法的基础上,引入纹理梯度各向异性算法,能够在避免纹理信息影响分割效果的前提下,最大限度地保证纹理边缘信息的完整。针对纹理特征数据敏感的特性,本文将离散的图像高度信息映射到连续的纹理梯度空间,能够有效减少由细小差异造成的过分割现象。结果 本文方法在BSD500 Dataset和Stanford Background Dataset中选择了大量的纹理信息丰富的图片与最新的分割算法进行了实验与对比。本文方法在分割效果（降低过分割现象）、保持边缘信息和分割准确率等方面均获得明显改进,并在图像分割的平均准确率方面与最新算法进行比较发现,本文算法的平均分割准确率达到90.9%,明显超过了其他最新算法,验证了本文方法的有效性。结论 本文提出的基于分水岭的纹理梯度各向异性算法对纹理图像的分割具有保边和准确的特点,采用连续梯度空间的方法能够有效地减少传统分水岭算法的过分割现象。本文方法主要适用于纹理信息丰富（自然纹理和人工纹理）的图片。     

A new geometric model for clustering high-resolution satellite images

Image segmentation is a central process in image processing. There are many segmentation methods such as region growing, edge detection, split and merge and artificial neural networks (ANNs). However, the most important and popular are clustering methods. Normally, clustering methods select cluster centres randomly to segment an image into disjoint and homogeneous regions. The use of random cluster centres without a priori knowledge leads to degradation in the accuracy of the obtained results. However, combined with edge detection, shape representation can help in improving the clustering methods. The improvement is obtained by knowing the optimal location of the cluster centres at the beginning of the image segmentation process. In this article, a new geometric model for high-resolution satellite image segmentation is implemented that can overcome the problem encountered in random clustering processes. The proposed model uses Canny–Deriche edge detection and the modified non-uniform rational B-spline (NURBS) methods to generate the control points of the edges. These points are used to identify cluster centres that are necessary to create the population of the hybrid dynamic genetic algorithm (HDGA). The new geometric model is compared with the self-organizing maps (SOMs) method, which is an efficient unsupervised ANN method. Two experiments are conducted using high-resolution satellite images, and the results prove the high accuracy and reliability of the new evolutionary geometric model.     

结合四元数与最小核值相似区的边缘检测

目的 针对传统彩色图像边缘检测方法中未充分利用图像色度信息、颜色模型间非线性转换过程中时间和空间的大量耗费、算法实现复杂等问题,将四元数引入最小核值相似区（SUSAN）算法中,提出一种RGB空间下的结合四元数与最小核值相似区的边缘检测算法。方法 该算法首先对彩色图像进行四元数描述,然后用改进的SUSAN算子进行边缘检测。针对其中单一几何阈值g的限制,以及检测出的边缘较粗等问题,本文采用Otsu算法自适应获取双几何阈值,再对弱边缘点集进行边缘生长,最后根据USAN重心及其对称最长轴来确定边缘局部方向,实现对边缘点的局部非极大值抑制,得到最终细化后的边缘图像。结果 实验选取1幅合成彩色图像及3幅标准图像库图像,与彩色Canny算法、SUSAN算法,及采用单阈值的本文算法进行对比,并采用Pratt品质因数衡量边缘定位精度。本文算法能够检测出亮度相近的不同颜色区域之间的边缘,且提取的边缘比较连续、细致,漏检边缘较少。与公认边缘检测效果较好的彩色Canny算法相比,本文算法的品质因数提高了0.012 0,耗时缩短了2.527 9 s。结论 本文提出了一种结合四元数与最小核值相似区的边缘检测算法,实现了四元数与SUSAN算子的有效融合。实验结果表明,该算法能够提高边缘定位精度,对弱噪声具有较好的抑制能力,适用于对实时性要求不高的低层次彩色图像处理。     

基于模糊增强的图像区域分割算法研究

针对图像平坦区、纹理区和清晰边缘的分割问题,提出了一种基于模糊增强的图像分割算法.该算法依据基于模糊增强的Canny边缘检测原理,在充分分析图像纹理区和清晰边缘的像素分布特点的基础上,通过增强纹理区像素对比度,检测出更多的纹理区细节.并利用膨胀、区域连通等方法实现了图像的区域分割.实验结果表明,该算法能够准确地实现了图像平坦区、纹理区和清晰边缘的分割,并有较强的抗噪能力.图像分割结果可以反映更多的纹理细节信息.     

A high performance edge detector based on fuzzy inference rules

Edge detection is an important topic in computer vision and image processing. In this paper, a novel edge detector based on fuzzy If-Then inference rules and edge continuity is proposed. The fuzzy If-Then rule system is designed to model edge continuity criteria. The maximum entropy principle is used in the parameter adjusting process. We also discuss the related issues in designing fuzzy edge detectors. We compare it with the popular edge detectors: Sobel and Canny edge detectors. The proposed fuzzy edge detector does not need parameter setting as Canny edge detector does, and it can preserve an appropriate detection in details. It is very robust to noise and can work well under high level noise situations, while other edge detectors cannot. The detector efficiently extracts edges in images corrupted by noise without requiring the filtering process. The experimental results demonstrate the superiority of the proposed method to existing ones.     

Detection and Segmentation of Multiple,Partially Occluded Objects by Grouping,Merging, Assigning Part Detection Responses

We propose a method that detects and segments multiple, partially occluded objects in images. A part hierarchy is defined for the object class. Both the segmentation and detection tasks are formulated as binary classification problem. A whole-object segmentor and several part detectors are learned by boosting local shape feature based weak classifiers. Given a new image, the part detectors are applied to obtain a number of part responses. All the edge pixels in the image that positively contribute to the part responses are extracted. A joint likelihood of multiple objects is defined based on the part detection responses and the object edges. Computation of the joint likelihood includes an inter-object occlusion reasoning that is based on the object silhouettes extracted with the whole-object segmentor. By maximizing the joint likelihood, part detection responses are grouped, merged, and assigned to multiple object hypotheses. The proposed approach is demonstrated with the class of pedestrians. The experimental results show that our method outperforms the previous ones.     

垃圾邮件图像中的文字角点检测

为提取垃圾邮件图像中文字的角点信息,提出一种新的基于图像边缘和圆形模板的角点检测算法。算法首先利用彩色边缘检测算子和阈值分割方法获取文字图像的边缘,然后采用圆形模板提取文字的角点信息。边缘检测和阈值分割降低了干扰背景和噪声对角点检测的影响,圆形模板使得角点检测对文字方向变化不敏感。实验表明,在真实的垃圾邮件图像中文字角点定位精度略高于SUSAN算法,并能同时获取角点角度的大小。     

Robust contour reconstruction of red blood cells and parasites in the automated identification of the stages of malarial infection

We present a novel method for detecting malaria parasites and determining the stage of infection from digital images comprising red blood cells (RBCs). The proposed method is robust under varying conditions of image luminance, contrast and clumping of RBCs. Both strong and weak boundary edges of the RBCs and parasites are detected based on the similarity measure between local image neighborhoods and predefined edge filters. A rule-based algorithm is applied to link edge fragments to form closed contours of the RBCs and parasite regions, as well as to split clumps into constituent cells. A radial basis support vector machine determines the stage of infection from features extracted from each parasite region. The proposed method achieves 97% accuracy in cell segmentation and 86% accuracy in parasite detection when tested on a total of 530 digitally captured images of three species of malaria parasites: Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei.     

结合分数阶微分和图像局部信息的CV模型

目的 由于CV模型仅利用了图像的全局信息,其对灰度不均匀图像的分割效果不理想,同时在分割弱边缘和弱纹理图像时,优化易陷入局部最优从而导致分割效率低下,且对初始位置的选择较为敏感。针对这些问题,提出一种结合分数阶微分和图像局部信息的CV模型。方法 首先将分数阶梯度信息融入图像的局部信息中,用来替代CV模型的整数阶全局信息,并建立自适应计算分数阶最佳阶次的数学模型,然后在模型中加入符号距离的约束项。结果 一方面,用局部信息代替全局信息,可以在一定程度上解决CV模型对灰度不均匀图像分割效果不理想的问题。另一方面,将Grünwald-Letnikov分数阶梯度信息融合到局部信息中,当分数阶阶次0 < α < 1时,增加了图像灰度不均匀、弱边缘、弱纹理区域的梯度信息,从而增加了演化驱动力避免演化曲线陷入局部最优,有效地解决了图像因灰度变化不大导致演化曲线驱动力小的问题,在一定程度上解决了模型对初始轮廓位置选择和对噪声敏感的问题。同时为了解决人工选取最佳分数阶阶次费时费力的问题,根据图像的梯度模值和信息熵建立计算分数阶最佳阶次的数学模型,将此自适应分数阶模型应用到算法之中,以自适应确定最佳分数阶阶次。此外,为了避免模型的重新初始化,在模型中加入符号距离的约束项,从而提高了曲线的演化效率。结论 理论分析和实验结果均表明,该算法能够较好地分割灰度不均匀、弱边缘和弱纹理区域的图像,并能根据图像特征自适应确定最佳分数阶阶次,提高了分割精度和分割效率,且对初始轮廓位置选择及噪声均具有一定的鲁棒性。     

Watershed-based hierarchical SAR image segmentation

Watershed transformation is a powerful image segmentation tool recently developed in mathematical morphology. In order to segment images initially oversegmented by watershed transformation, two approaches are considered: one is the thresholding of the gradient image proposed by us which is capable of keeping more salient image contours; the other is the well known centroid linkage region growing algorithm which merges regions with certain statistical similarities. By choosing suitable thresholds in the two approaches, hierarchical image segmentation algorithms can be constructed. A Ratio of Averages (ROA) edge detector is proposed to replace the morphological edge detectors prior to watershed transformation when applied to Synthetic Aperture Radar (SAR) images. Applications to SAR agricultural image segmentation with these hierarchical segmentation algorithms are presented. It is demonstrated that the algorithms are efficient in the segmentation of the SARimages and appropriate for land use applications when the land cover is made up of individual plots.     

Edge detection and linear feature extraction using a 2-D randomfield model

The edge-detection problem is posed as one of detecting step discontinuities in the observed correlated image, using directional derivatives estimated with a random field model. Specifically, the method consists of representing the pixels in a local window by a 2-D causal autoregressive (AR) model, whose parameters are adaptively estimated using a recursive least-squares algorithm. The directional derivatives are functions of parameter estimates. An edge is detected if the second derivative in the direction of the estimated maximum gradient is negatively sloped and the first directional derivative and a local estimate of variance satisfy some conditions. Because the ordered edge detector may not detect edges of all orientations well, the image scanned in four different directions, and the union of the four edge images is taken as the final output. The performance of the edge detector is illustrated using synthetic and real images. Comparisons to other edge detectors are given. A linear feature extractor that operates on the edges produced by the AR model is presented     

基于肤色质心与边缘自生长的手势分割算法

针对现有手势分割方法难以在类肤色背景下从图像中高效完整地分割出静态手势的问题,提出一种基于肤色质心与边缘自生长的手势分割算法。利用肤色模型得到手势区域的质心,质心可降低后续边缘检测算法的计算量;利用改进的边缘检测算法得到手势边缘,同时提出一种边缘自生长算法,能有效补全局部断裂边缘,增强后续分割效果;将肤色信息与边缘信息进行差分运算分离类肤色背景,再用连通域及形态学处理去除以得到最终手势图像。实验结果证明,该算法较传统肤色模型及同类算法,能更加快速准确地在类肤色背景下分割出手势图像。