NMR image segmentation based on Unsupervised Extreme Learning Machine

Unsupervised Extreme Learning Machine (US-ELM) is a machine learning method widely used. With good performance in anti-noise and data representation, as well as fast clustering speed, US-ELM is suitable for processing noise containing nuclear magnetic resonance (NMR) image. Therefore, in this paper, a brain NMR image segmentation approach based on US-ELM is proposed. Firstly, a median filter is adopted to reduce the influence of noise; Secondly, US-ELM maps the original data into the embedded space, which makes it increasingly effective to represent the characteristic of pixel points, and then uses the k-means method to perform the image segmentation, named NS-UE; After that, spatial fuzzy C-means (spFCM) provides a better solution for handling NMR image with noise caused by the intensity inhomogeneity than k-means does. As a result, an image segmentation approach based on US-ELM and spFCM (NS-UF) is proposed, so as to improve the effect of clustering in embedded space. Finally, extensive experiments on real data demonstrated the efficiency and effectiveness of our proposed approaches with various experimental settings.     

Unsupervised segmentation based on robust estimation and color active contour models.

One of the most commonly used clinical tests performed today is the routine evaluation of peripheral blood smears. In this paper, we investigate the design, development, and implementation of a robust color gradient vector flow (GVF) active contour model for performing segmentation, using a database of 1791 imaged cells. The algorithms developed for this research operate in Luv color space, and introduce a color gradient and L2E robust estimation into the traditional GVF snake. The accuracy of the new model was compared with the segmentation results using a mean-shift approach, the traditional color GVF snake, and several other commonly used segmentation strategies. The unsupervised robust color snake with L2E robust estimation was shown to provide results which were superior to the other unsupervised approaches, and was comparable with supervised segmentation, as judged by a panel of human experts.     

彩色空间的视频对象自动分割

提出了一种基于RGB空间的视频对象自动分割方法。图像简化阶段,采用连接算子中的区域开启闭合算子来简化图像;图像标识提取阶段利用RGB空间的信息得到准确的视频对象轮廓,根据对比度消除区域中噪声小梯度,并在此基础上提取标识,在分水岭阶段,采用类似区域增长的改进分水岭方法,实验证明此方法的结果准确可靠。     

基于Munsell-HLC颜色空间的彩色图像分割

图像分割既是数字图像处理中的主要研究内容之一,也是进一步进行图像识别、分析和理解的基础。目前,灰度图像分割算法已经比较成熟,随着彩色图像在各个领域的广泛应用,出现了许多用来进行彩色图像分割的颜色空间和色差的理论。这里用HLC颜色空间及颜色距离（色差）实现彩色图像分割,实验结果证明了这种方法的有效性。     

基于支持向量机的彩色图像分割研究

为了提高彩色图像分割方法的性能,提出一种基于支持向量机的手动选择样本点集的分割方法。该方法通过人为主观观察颜色特征变化,在像素峰值处选择样本点,使得背景和目标样本点的颜色差异较明显,达到了简化样本点的目的,从而实现了彩色图像的快速分割,同时比较和分析核函数参数及样本点数目的不同对分割效果的影响。实验证明,与传统的窗口取样相比,该方法更加的快速有效,且算法简单,易于推广。     

基于HSI色彩坐标相似度的彩色图像分割方法

该文提出一种基于HSI彩色空间的图像分割方法。欧氏距离作为图像分割中常用的衡量像素点之间彩色关系的依据,在HSI坐标系下却不能很好地反应两个像素点之间的关系。因此,提出相似度代替欧氏距离作为一种新的衡量两个像素点之间彩色关系的依据。算法通过确定HSI分量中占主导地位的分量,建立彩色图像分割模型,创建一个和原图尺寸一样的颜色相似度等级图,并利用相应的颜色相似度等级图的颜色信息对像素点进行聚类。实验结果表明,所提出的分割算法具有很强的鲁棒性和准确性,在其他条件相同的情况下,基于相似度的分割方法优于基于欧氏距离为基准的彩色图像分割。     

Unsupervised Bayesian image segmentation using orthogonal series

This paper deals with the problem of unsupervised image segmentation which consists in first mixture identification phase and second a Bayesian decision phase. During the mixture identification phase, the conditional probability density function (pdf) and the a priori class probabilities must be estimated. The most difficult part is the estimation of the number of pixel classes or in other words the estimation of the number of density mixture components. To resolve this problem, we propose here a Stochastic and Nonparametric Expectation-Maximization (SNEM) algorithm. The algorithm finds the most likely number of classes, their associated model parameters and generates a segmentation of the image by classifying the pixels into these classes. The non-parametric aspect comes from the use of the orthogonal series estimator. Experimental results are promising, we have obtained accurate results on a variety of real images.     

基于遗传算法的彩色图像多阈值分割方法研究

针对彩色图像多阈值分割中阈值个数自动确定困难和优化时间长的问题,首先提出一种新的HSV空间中彩色图像投影预处理方法,然后计算待分割图像的颜色粗糙度,并根据颜色粗糙度确定图像分割的阈值数量,为提高分割效率,利用遗传算法搜索最优分割阈值组合,为提高分割精度,在遗传算法适应度函数设计时既考虑了类内的颜色离散度,又考虑了像素的空间关系。实验结果表明该方法具有较为理想的分割效果,对光线变化具有较好的鲁棒性。     

基于颜色特征判别的纸病图像分割研究

针对当前纸病检测中图像分割算法的精确性及抗干扰性问题,文中提出了一种基于颜色特征判别的纸病图像分割算法。首先建立RGB颜色空间模型,提取空间分量信息特征,然后分别对RGB图像的3个通道的像素值进行可靠性计算,最后通过逻辑"或"运算融合单通道的计算结果,得到分割图像。结果表明:该算法定位准确、抗干扰性强,能够精确分割纸病图像,满足纸病检测要求。     

Unsupervised contour closure algorithm for range image edge-based segmentation.

This paper presents an efficient technique for extracting closed contours from range images' edge points. Edge points are assumed to be given as input to the algorithm (i.e., previously computed by an edge-based range image segmentation technique). The proposed approach consists of three steps. Initially, a partially connected graph is generated from those input points. Then, the minimum spanning tree of that graph is computed. Finally, a postprocessing technique generates a single path through the regions' boundaries by removing noisy links and closing open contours. The novelty of the proposed approach lies in the fact that, by representing edge points as nodes of a partially connected graph, it reduces the contour closure problem to a minimum spanning tree partitioning problem plus a cost function minimization stage to generate closed contours. Experimental results with synthetic and real range images, together with comparisons with a previous technique, are presented.     

LS-SVM based image segmentation using color and texture information

Image segmentation partitions an image into nonoverlapping regions, which ideally should be meaningful for a certain purpose. Automatic segmentation of images is a very challenging fundamental task in computer vision and one of the most crucial steps toward image understanding. In recent years, many image segmentation algorithms have been developed, but they are often very complex and some undesired results occur frequently. In this paper, we present an effective color image segmentation approach based on pixel classification with least squares support vector machine (LS-SVM). Firstly, the pixel-level color feature, Homogeneity, is extracted in consideration of local human visual sensitivity for color pattern variation in HSV color space. Secondly, the image pixel’s texture features, Maximum local energy, Maximum gradient, and Maximum second moment matrix, are represented via Gabor filter. Then, both the pixel-level color feature and texture feature are used as input of LS-SVM model (classifier), and the LS-SVM model (classifier) is trained by selecting the training samples with Arimoto entropy thresholding. Finally, the color image is segmented with the trained LS-SVM model (classifier). This image segmentation not only can fully take advantage of the local information of color image, but also the ability of LS-SVM classifier. Experimental evidence shows that the proposed method has very effective segmentation results and computational behavior, and decreases the time and increases the quality of color image segmentation in comparison with the state-of-the-art segmentation methods recently proposed in the literature.     

Unsupervised image segmentation based on analysis of binary partition tree for salient object extraction

This paper proposes an unsupervised image segmentation approach aimed at salient object extraction. Starting from an over-segmentation result of a color image, region merging is performed using a novel dissimilarity measure considering the impact of color difference, area factor and adjacency degree, and a binary partition tree (BPT) is generated to record the whole merging sequence. Then based on a systematic analysis of the evaluated BPT, an appropriate subset of nodes is selected from the BPT to represent a meaningful segmentation result with a small number of segmented regions. Experimental results demonstrate that the proposed approach can obtain a better segmentation performance from the perspective of salient object extraction.     

应用颜色信息的图像分割研究

提出了一种在RGB颜色空间中颜色距离定义的方式,并根据颜色距离,用Roberts梯度算子得到颜色距离直方图,确定图像边缘信息的阈值。通过Roberts算子,使用此阈值得到图像的边缘信息。这种方式,充分考虑了图像中的颜色信息,与灰度图的处理方式相比,减少了计算量,提高了具有相似亮度的不同颜色之间边缘信息的提取成功率。     

Unsupervised vector image segmentation by a tree structure-ICM algorithm

In recent years, many image segmentation approaches have been based on Markov random fields (MRFs). The main assumption of the MRF approaches is that the class parameters are known or can be obtained from training data. In this paper the authors propose a novel method that relaxes this assumption and allows for simultaneous parameter estimation and vector image segmentation. The method is based on a tree structure (TS) algorithm which is combined with Besag's iterated conditional modes (ICM) procedure. The TS algorithm provides a mechanism for choosing initial cluster centers needed for initialization of the ICM. The authors' method has been tested on various one-dimensional (1-D) and multidimensional medical images and shows excellent performance. In this paper the authors also address the problem of cluster validation. They propose a new maximum a posteriori (MAP) criterion for determination of the number of classes and compare its performance to other approaches by computer simulations.     

Unsupervised regions based segmentation using object discovery

We present a new unsupervised algorithm to discovery and segment out common objects from multiple images. Compared with previous cosegmentation methods, our algorithm performs well even when the appearance variations in the foregrounds are more substantial than those in some areas of the backgrounds. Our algorithm mainly includes two parts: the foreground object discovery scheme and the iterative region allocation algorithm. Two terms, a region-saliency prior and a region-repeatness measure, are introduced in the foreground object discovery scheme to detect the foregrounds without any supervisory information. The iterative region allocation algorithm searches the optimal solution for the final segmentation with the constraints from a maximal spanning tree, and an effective color-based model is utilized during this process. The comparative experimental results show that the proposed algorithm matches or outperforms several previous methods on several standard datasets.     

Unsupervised variational image segmentation/classification using a Weibull observation model.

Studies have shown that the Weibull distribution can model accurately a wide variety of images. Its parameters index a family of distributions which includes the exponential and approximations of the Gaussian and the Raleigh models widely used in image segmentation. This study investigates the Weibull distribution in unsupervised image segmentation and classification by a variational method. The data term of the segmentation functional measures the conformity of the image intensity in each region to a Weibull distribution whose parameters are determined jointly with the segmentation. Minimization of the functional is implemented by active curves via level sets and consists of iterations of two consecutive steps: curve evolution via Euler-Lagrange descent equations and evaluation of the Weibull distribution parameters. Experiments with synthetic and real images are described which verify the validity of method and its implementation.     

A multiscale random field model for Bayesian image segmentation

Many approaches to Bayesian image segmentation have used maximum a posteriori (MAP) estimation in conjunction with Markov random fields (MRF). Although this approach performs well, it has a number of disadvantages. In particular, exact MAP estimates cannot be computed, approximate MAP estimates are computationally expensive to compute, and unsupervised parameter estimation of the MRF is difficult. The authors propose a new approach to Bayesian image segmentation that directly addresses these problems. The new method replaces the MRF model with a novel multiscale random field (MSRF) and replaces the MAP estimator with a sequential MAP (SMAP) estimator derived from a novel estimation criteria. Together, the proposed estimator and model result in a segmentation algorithm that is not iterative and can be computed in time proportional to MN where M is the number of classes and N is the number of pixels. The also develop a computationally efficient method for unsupervised estimation of model parameters. Simulations on synthetic images indicate that the new algorithm performs better and requires much less computation than MAP estimation using simulated annealing. The algorithm is also found to improve classification accuracy when applied to the segmentation of multispectral remotely sensed images with ground truth data.     

基于最小生成树和局部阈值的彩色图像分割方法

针对分水岭图像分割算法对于彩色图像的过度分割问题,本文提出一种基于最小生成树和局部阈值的解决方法。该方法主要利用图论中的最小生成树,对分水岭算法产生的过度分割区域进行合并。与其它的基于最小生成树的方法不同,该方法只有当构造出一棵完整的最小生成树时,才能计算出一个局部阈值,该局部阈值可确定原构造最小生成树过程的终止条件,进而可分割出彩色图像中的两个区域。重复上述过程,可分割出原彩色图像中的所有区域。实验证明,本文方法能够对彩色图像进行准确的分割,并且分割结果能很好地符合人眼的感知。