基于鱼群算法的图像阈值分割*

本文提出了一种基于鱼群算法的二维阈值图像分割的新方法。传统的二维Otsu方法考虑了图像的灰度信息和像素间的空间邻域信息,是一种有效的图像分割方法。针对Ostu方法的计算量大、运行时间长的缺陷,采用鱼群算法来搜索最优二维阈值向量,通过鱼群追尾行为获得最优阈值。实验结果表明,所提出的方法不仅能得到理想的分割结果,而且分割速度快。     

Segmentation fusion based on neighboring information for MR brain images

In this paper, we study on how to boost image segmentation algorithms. First of all, a novel fusion scheme is proposed to combine different segmentations with mutual information to reduce misclassified pixels and obtain an accurate segmentation. As the class label of each pixel depends on the pixel’s gray level and neighbors’ labels, the fusion scheme takes both spatial and intensity information of pixels into account. Then, a detail thresholding segmentation case is designed using the proposed fusion scheme. In the case, the local Laplacian filter is used to get the smoothed version of original image. To accelerate segmentation, a discrete curve evolution based Otsu method is employed to segment the original image and its smoothed version to get two different segmentation maps. The fusion scheme is used to fuse the two maps to get the final segmentation result. Experiments on medical MR-T2 brain images are conducted to demonstrate the effectiveness of the proposed segmentation fusion method. The experimental results indicate that the proposed algorithm can improve segmentation accuracy and it is superior to other multilevel thresholding methods.     

A Local Contrast Fusion Based 3D Otsu Algorithm for Multilevel Image Segmentation

To overcome the shortcomings of 1D and 2D Otsu’s thresholding techniques, the 3D Otsu method has been developed. Among all Otsu’s methods, 3D Otsu technique provides the best threshold values for the multi-level thresholding processes. In this paper, to improve the quality of segmented images, a simple and effective multilevel thresholding method is introduced. The proposed approach focuses on preserving edge detail by computing the 3D Otsu along the fusion phenomena. The advantages of the presented scheme include higher quality outcomes, better preservation of tiny details and boundaries and reduced execution time with rising threshold levels. The fusion approach depends upon the differences between pixel intensity values within a small local space of an image; it aims to improve localized information after the thresholding process. The fusion of images based on local contrast can improve image segmentation performance by minimizing the loss of local contrast, loss of details and gray-level distributions. Results show that the proposed method yields more promising segmentation results when compared to conventional 1D Otsu, 2D Otsu and 3D Otsu methods, as evident from the objective and subjective evaluations.      

基于广义调和均值距离的图像分割新算法

提出了基于广义调和均值距离的最小偏差图像阈值化分割新算法。Otsu阈值法是图像分割中最典型阈值法之一,因其计算简单、速度快和性能稳定等优点而在图像分割中得到广泛应用;但是,传统Otsu阈值法是基于欧式距离的最小偏差阈值法,由于欧式距离没有可调节参数而导致Otsu阈值法分割图像缺乏鲁棒性。首先将Otsu图像分割法中的欧式距离用广义调和均值距离代替并得到一种具有鲁棒性的图像分割新算法,其次给出该算法中参数选取办法。大量实验结果表明,新的图像分割算法相比Otsu法更有效。     

二维Otsu阈值法的快速算法

最大类间方差法(Otsu)是图像分割的经典算法,在其基础之上发展起来的二维Otsu阈值分割法由于计算复杂而制约了其应用。针对这一缺点,提出一种改进的二维Otsu阈值法的快速算法。首先将原始二维直方图划分成M×M个区域,将每个区域视为1个点,构造新的二维直方图,在其上利用二维Otsu以及快速递推算法,得到分割阈值所处的区域编号;既而对所确定的区域再次使用二维Otsu算法得到原始图像的分割阈值。实验结果证明,改进算法有效地提高了计算速度,降低了算法的空间复杂度,且分割效果与原始算法基本一致。     

自适应最小误差阈值分割算法

对二维最小误差法进行三维推广, 并结合三维直方图重建和降维思想提出了一种鲁 棒的最小误差阈值分割算法. 但该方法为全局算法, 仅适用于分割均匀光照图像. 为 提高其自适应性, 本文采用Water flow模型对非均匀光照图像进行背景估计, 以此获 得原始图像与背景图像的差值图像, 达到降低非均匀光照对图像分割造成干扰的目的. 为进 一步提高分割性能, 本文对差值图像采用γ 矫正进行增强, 然后采用鲁棒最小误差 法进行全局分割, 从而完成目标提取. 最后本文对均匀光照下以及非均匀光照下图像进行了 实验, 并与一维最小误差法、二维最小误差法、三维直方图重建和降维的Otsu阈值分割 算法、灰度波动变换自适应阈值方法以及一种改进的FCM方法在错误分割率和运行时间上进 行了对比. 实验结果表明, 相对于以上方法, 本算法的分割性能均有明显提升.     

基于颜色特征的玉米雄穗图像分割

提出了一种基于颜色特征的玉米雄穗分割方法.利用侧抑制网络与二维Otsu结合的分割方法对玉米雄穗图像的YCbCr颜色空间的Cr分量进行分割,再利用相同方法对玉米雄穗图像的超绿特征图像进行分割,取两个分割结果的交集,去除小面积的连通域,得到玉米雄穗的分割图.为了验证算法的有效性,选用了不同生长环境的玉米雄穗图像,分别利用本文方法、二维Otsu和基于侧抑制的二维Otsu方法进行了比较实验.结果表明:该方法有很好的抗干扰性,对生长环境有很强的鲁棒性.     

狼群优化的二维Otsu快速图像分割算法

传统二维Otsu算法的阈值选取大都采用穷尽搜索方式,造成算法分割时间较长、实时性差等缺点,影响图像分割效果。为提高算法的运行效率,采用狼群算法来搜索最优阈值,每匹人工狼代表一个可行的二维阈值向量,狼群通过游走、召唤、围攻这三种智能行为的不断迭代以及狼群间的信息交互来获取最佳阈值。仿真结果表明,与标准粒子群优化二维Otsu算法和传统二维Otsu算法相比,狼群优化算法降低了分割时间并提高了图像分割精度。     

基于蚁群算法的改进Otsu理论的图像多阈值分割

图像分割是由图像处理到图像分析的关键步骤,Otsu法是一种效果较好、实现简单的阈值分割方法。针对传统的Otsu阈值计算方法耗时较多、准则函数不一定单峰这一问题,提出了采用蚁群优化算法来求解阈值,并改进了传统的Otsu理论。分割效果表明该算法不仅提高了分割质量,而且缩短了寻优时间,从而说明了该算法的有效性,正确性。     

基于图像边缘信息的2维阈值分割方法

为了改善2维阈值分割性能,提高图像分割的效率,在传统2维Otsu阈值分割算法的基础上,提出了一种基于图像边缘信息的2维阈值分割方法。这种改进的方法保留了2维Otsu阈值分割算法分割结果准确的优点,并在此基础上充分利用图像的边缘信息,通过分析图像的边缘直方图和阈值的关系来得到最优分割阈值。仿真实验结果表明,该方法与传统2维分割算法相比,不仅计算简单,而且实时性好。     

Multi-level image thresholding using Otsu and chaotic bat algorithm

Multi-level thresholding is a helpful tool for several image segmentation applications. Evaluating the optimal thresholds can be applied using a widely adopted extensive scheme called Otsu’s thresholding. In the current work, bi-level and multi-level threshold procedures are proposed based on their histogram using Otsu’s between-class variance and a novel chaotic bat algorithm (CBA). Maximization of between-class variance function in Otsu technique is used as the objective function to obtain the optimum thresholds for the considered grayscale images. The proposed procedure is applied on a standard test images set of sizes (512 × 512) and (481 × 321). Further, the proposed approach performance is compared with heuristic procedures, such as particle swarm optimization, bacterial foraging optimization, firefly algorithm and bat algorithm. The evaluation assessment between the proposed and existing algorithms is conceded using evaluation metrics, namely root-mean-square error, peak signal to noise ratio, structural similarity index, objective function, and CPU time/iteration number of the optimization-based search. The results established that the proposed CBA provided better outcome for maximum number cases compared to its alternatives. Therefore, it can be applied in complex image processing such as automatic target recognition.

     

数字图像处理等；基于二维Otsu和模糊聚类的图像分割算法*

针对传统二维Otsu算法计算复杂度高的问题,提出一种改进的Otsu图像分割算法。该算法通过求两个一维Otsu法的阈值来代替传统二维Otsu法的阈值,使得计算复杂度得到了降低;同时为了改进分割效果,结合使用了模糊C-均值聚类算法。实验结果表明,改进的算法充分发挥了两者的优势,不仅在计算速度上优于原二维Otsu算法,且分割效果较好。     

改进的遗传算法在医学图像中的应用

针对标准的遗传算法（ GA）在优化Otsu法求取图像阈值时出现收敛速度慢、易早熟等问题,提出了一种改进的GA用于图像分割。该算法根据种群不同的进化代数和个体适应度的大小,动态地调整精英选择策略和遗传算子,从而提高了算法的收敛速度、得到了范围稳定的图像分割阈值,且保持了种群多样性。将该算法应用于医学图像分割,实验结果表明：该算法可以对医学图像进行分割且效果明显。     

Multi-objective and multi-level image thresholding based on dominance and diversity criteria

The Kapur and Otsu methods are widely used image thresholding approaches and they are very efficient in bi-level thresholding applications. Evolutionary algorithms have been developed to extend the Kapur and Otsu methods to the multi-level thresholding case. However, there remains an unsolved argument that neither Kapur nor Otsu objective can optimally fit diverse content contained in different kinds of images. This paper proposes a multi-objective model which seeks to find the Pareto-optimal set with respect to Kapur and Otsu objectives. Based on dominance and diversity criteria, we developed a hybrid multi-objective particle swarm optimization (MOPSO) method by incorporating several intelligent search strategies. The ensemble strategy is also applied to automatically select the best search strategy to perform at various algorithm stages according to its historic performances. The experimental result shows that the solutions to our multi-objective model consistently produce equal or better segmentation results than those by the optimal solutions to the original Kapur and Otsu models, and that the proposed hybrid algorithm with and without the ensemble strategy produces a better approximation to the ideal Pareto front than those obtained by two other MOPSO variants and the MOEA/D. In comparison with the most recent multilevel thresholding methods, our approach also consistently obtains better performance in the segmentation result for several benchmark images.     

A new active contour remote sensing river image segmentation algorithm inspired from the cross entropy

The CV (Chan–Vese) model is a piecewise constant approximation of the Mumford and Shah model. It assumes that the original image can be segmented into two regions such that each region can be represented as constant grayscale value. In fact, the objective functional of the CV model actually finds a segmentation of the image such that the within-class variance is minimized. This is equivalent to the Otsu image thresholding algorithm which also aims to minimize the within-class variance. Similarly to the Otsu image thresholding algorithm, cross entropy is another widely used image thresholding algorithm and it finds a segmentation such that the cross entropy of the segmented image and the original image is minimized. Inspired from the cross entropy, a new active contour image segmentation algorithm is proposed. The region term in the new objective functional is the integral of the logarithm of the ratio between the grayscale of the original image and the mean value computed from the segmented image weighted by the grayscale of the original image. The new objective functional can be solved by the level set evolution method. A distance regularized term is added to the level set evolution equation so the level set need not be reinitialized periodically. A fast global minimization algorithm of the objective functional is also proposed which incorporates the edge term originated from the geodesic active contour model. Experimental results show that, the algorithm proposed can segment images more accurately than the CV model and the implementation speed of the fast global minimization algorithm is fast.     

基于小波分层的多方向医学CT图像增强算法

结合先进的小波理论,时医学CT图像进行小波多尺度变换,得到具有方向性的分量.把改进的小波阙值法与基于小波的同态滤波结合起来分别与这些分量对应起来进行增强,最后分别得到不同尺度(层次)增强的图像,再进一步合成,得到较好的增强效果.实验结果表明,采用该算法可对图像去除噪声的同时能很好的保留图像的重要特征,达到增强医学CT图像的效果.     

基于双界线的Otsu阈值分割法及其快速算法

传统2维Otsu阈值分割法由于运算时间长、抗噪能力不足而在应用中受到限制。为了克服这些缺点,提出了一种基于双界线的2维Otsu阈值理论及其快速算法。在新的2维直方图中,两条平行于对角线的界线决定目标和背景区域的宽度,垂直于对角线的分割直线决定阈值大小。该算法运用Roberts算子和线性拟合法确定双界线,然后运用改进的Otsu法计算最佳阈值,最后对噪声区域进行后处理。实验结果表明,该算法不仅运算速度快,而且具备较好的分割质量和抗噪性能。同时,快速算法的引入,进一步降低了运算量,使得该算法具备更好的实时性。     

改进的二维最小卡方散度图像分割方法

传统的交叉熵阈值法具有抗噪性能差,计算时间长等问题。为了改进算法的性能,提出了一种二维最小卡方散度图像阈值化分割新准则,构建了基于改进中值滤波的新型二维直方图。利用对称卡方散度描述分割前后图像之间的差异程度。使用关键阈值对滤波图像进行分割,达到最佳的分割效果。实验结果表明,与二维Otsu和二维最小交叉熵法相比,提出的方法不仅大大缩短了分割时间,而且分割性能与抗噪性能更强。     

一种改进粒子群优化算法的Otsu图像阈值分割方法

阈值法分割图像时只利用图像的灰度信息,具有直观、实现简单的特点。针对传统的粒子群优化算法(Particle Swarm Optimization,PSO)分割图像易陷入局部最优的缺点,提出一种基于改进粒子群优化算法的Otsu图像阈值分割方法。以Otsu算法的类间方差作为适应度函数,在每次迭代中选取适应度较好的粒子同时加入新的粒子,以提高粒子多样性。实验表明,与Otsu算法和PSO算法相比,改进的粒子群优化算法不仅加快了收敛速度和运算速度,而且提高了图像分割的准确率。     

Skin cancer extraction with optimum fuzzy thresholding technique

This paper discusses a new approach to segment different types of skin cancers using fuzzy logic approach. The traditional skin cancer segmentation involves the analysis of image features to delineate the cancerous region from the normal skin. Using low level features such as colour and intensity, segmentation can be done by obtaining a threshold level to separate the two regions. Methods like Otsu optimisation provide a quick and simple process to optimise such threshold level; however this process is prone to the lighting and skin tone variations. Fuzzy clustering algorithm has also been widely used in image processing due to its ability to model the fuzziness of human visual perception. Classical fuzzy C means (FCM) clustering algorithm has been applied to image segmentation with good results; however, the classical FCM is based on type-1 fuzzy sets and is unable to handle uncertainties in the images. In this paper, we proposed an optimum threshold segmentation algorithm based on type-2 fuzzy sets algorithms to delineate the cancerous area from the skin images. By using the 3D colour constancy algorithm, the effect of colour changes and shadows due to skin tone variation in the image can be significantly reduced in the preprocessing stage. We applied the optimum thresholding technique to the preprocessed image over the RGB channels, and combined individual results to achieve the overall skin cancer segmentation. Compared to the Otsu algorithm, the proposed method is less affected by the shadows and skin tone variations. The results also showed more tolerance at the boundary of the cancerous area. Compared with the type-1 FCM algorithm, the proposed method significantly reduced the segmentation error at the normal skin regions.