Multilevel thresholding using grey wolf optimizer for image segmentation

Multilevel thresholding is one of the most important areas in the field of image segmentation. However, the computational complexity of multilevel thresholding increases exponentially with the increasing number of thresholds. To overcome this drawback, a new approach of multilevel thresholding based on Grey Wolf Optimizer (GWO) is proposed in this paper. GWO is inspired from the social and hunting behaviour of the grey wolves. This metaheuristic algorithm is applied to multilevel thresholding problem using Kapur's entropy and Otsu's between class variance functions. The proposed method is tested on a set of standard test images. The performances of the proposed method are then compared with improved versions of PSO (Particle Swarm Optimization) and BFO (Bacterial Foraging Optimization) based multilevel thresholding methods. The quality of the segmented images is computed using Mean Structural SIMilarity (MSSIM) index. Experimental results suggest that the proposed method is more stable and yields solutions of higher quality than PSO and BFO based methods. Moreover, the proposed method is found to be faster than BFO but slower than the PSO based method.     

Automatic grey level thresholding through index of fuzziness and entropy

Algorithms for automatic thresholding of grey levels (without reference to histogram) are described using the terms ‘index of fuzziness’ and ‘entropy’ of a fuzzy set. Their values are seen to be minimum when the crossover point of an S-function corresponds to boundary levels among different regions in image space. The effectiveness of the algorithms is demonstrated for images having both bimodal and multimodal grey level distributions.     

HVS:构造一个虚拟实景空间

虚拟实景空间是指以实景图像或视频为素材构造出的虚拟空间.与传统的以三维造型为素材,由计算机实时绘制出的虚拟空间相比,虚拟实景空间不需要复杂的三维造型,对计算机计算能力要求低.虚拟实景空间支持用户在其中前进、后退、仰视、俯视、360度环视等操作.总结了虚拟实景空间构造系统HVS的空间模型与部分关键技术.     

一种基于HVS的数字水印算法

数字水印对于版权保护是一种很好的方法。文章根据人类视觉特性（HVS）,提出了一种包含水印嵌入与提取的数字水印算法,并给出了攻击分析。其中,采用图象作为数字水印,具有二维信号可视化的优点。实验表明,该算法对于有损压缩、剪切与噪声叠加等操作具有很好的鲁棒性。     

A novel histogram transformation to improve the performance of thresholding methods in edge detection

The gradient image is used to detect edge points, and the gradient histogram is a typical case of a unimodal histogram. It is well-documented that bi-modal thresholding methods (such as the Otsu method) detect edges poorly. Therefore, specific unimodal thresholding methods are used to detect edge points. However, unimodal thresholding methods (such as the Rosin method) sometimes obtain very noisy results. In this paper, we propose a histogram transformation to improve the performance of some thresholding methods. Using the Berkeley Segmentation Dataset, we present quantitative performance results in an edge detection task to show that our transformation improves the performance of the Otsu and Rosin methods. Our histogram transformation can be used by any histogram thresholding method, but the performance of the method, using the transformed histogram, will depend of the criterion used by this method.     

虚拟实景空间系统HVS的研究与实现

虚拟实景空间系统ＨＶＳ由计算机自动拼接,变形与组织许多幅离散的实景图像或连续的视频,生成虚拟空间。这种虚拟空间具有照片质量的视觉效果,称为虚拟实景空间。虑拟实景空间能为用户提供前进,后退,仰视,俯视,３６０度环视,近看,远看等漫游能力,可运行于ＰＣ平台,ＨＶＳ是虚拟实景空间的生成与漫游平台。将介绍它的模型,组成与实现。     

一种基于HVS的小波域水印算法

将有意义的二值图像作为水印图像,运用Arnold变换进行置乱加密,结合人眼视觉系统特性(HVS),对栽体图像小波系数进行计算以得到自适应的量化步长,以该步长对水平子带HL和垂直子带LH的小波系数进行量化,并把量化误差平均分配到这两个系数上,在保证嵌入强度的同时减少图像失真.水印提取时不需要原始载体图像和水印.实验结果证明本文提出的水印算法具有较好的不可见性和鲁棒性.     

一种基于FCM和HVS的隐写方法

为了提供较大的秘密信息嵌入量并保持良好的载密图像质量,提出了一种基于FCM（模糊聚类）和HVS（人眼视觉特性）的图像隐写方法。该方法将对比度和梯度敏感度作为特征向量,并通过模糊C均值聚类将像素分为视觉敏感类与视觉不敏感类;采用模算子隐写法将较多秘密信息嵌入属于视觉不敏感类的像素,而将较少秘密信息嵌入属于视觉敏感类的像素。实验结果表明,与SMFH方法相比,该方法具有更大的嵌入量。     

基于混沌加密和HVS的数字水印

将混沌加密理论运用于水印嵌入算法中,对水印图像进行先置乱再加密的预处理.结合DC分量和AC分量的优点在DC系数、AC低频系数和AC中低频系数上分别嵌入水印,并结合人类视觉系统的纹理掩蔽特性将原始图像块分为三类以控制水印的嵌入强度,实现水印的自适应嵌入.水印提取时,对结果进行融合来获得更好的提取效果.实验结果证明本算法具有良好的不可见性和鲁棒性.     

一种基于HVS的各向异性扩散去块效应算法

基于分块的离散余弦变换（BDCT）在众多的国际图像、视频压缩标准中是一种主要的压缩算法,它的一个主要不足就是在低比特率下会出现明显的方块效应。根据人类视觉系统的特性提出一个各向异性扩散系数模型,并且引进了扩散速率因子。实验结果表明该算祛能够有效地去除方块效应,同时又能保护图像的边缘信息。     

A survey of thresholding techniques

In digital image processing, thresholding is a well-known technique for image segmentation. Because of its wide applicability to other areas of the digital image processing, quite a number of thresholding methods have been proposed over the years. In this paper, we present a survey of thresholding techniques and update the earlier survey work by Weszka (Comput. Vision Graphics & Image Process 7, 1978, 259–265) and Fu and Mu (Pattern Recognit. 13, 1981, 3–16). We attempt to evaluate the performance of some automatic global thresholding methods using the criterion functions such as uniformity and shape measures. The evaluation is based on some real world images.     

A thresholding method based on two-dimensional Renyi's entropy

In this paper, we present a new thresholding technique based on two-dimensional Renyi's entropy. The two-dimensional Renyi's entropy was obtained from the two-dimensional histogram which was determined by using the gray value of the pixels and the local average gray value of the pixels. This new method extends a method due to Sahoo et al. (Pattern Recognition 30 (1997) 71) and includes a previously proposed global thresholding method due to Abutaleb (Pattern Recognition 47 (1989) 22). Further, our method extends a global thresholding method due to Chang et al. (IEEE Trans. Image Process. 4 (1995) 370) to the two-dimensional setting. The effectiveness of the proposed method is demonstrated by using examples from the real-world and synthetic images.     

基于多分辨率和HVS的盲图像水印隐藏方法

文章提出了一种盲图像水印隐藏方法,结合了人类视觉系统（ ＨＶＳ）和图像的 ＤＷＴ多分辨分解,实验结果表明这个方法是有效的。     

基于余切函数变换的区间灰数预测模型

针对区间灰数灰色预测问题,考虑区间灰数序列可能的4种情形,运用余切函数变换对不同情形的区间灰数序列分别进行处理,分别建立区间灰数的灰色预测模型,从而将灰色数据变换技术的应用范围扩展到区间灰数预测领域.最后,通过算例和实例分析验证了新模型的实用性和有效性.     

基于CDMA和HVS的多用户数字水印算法

针对多人共享版权时,需要同时嵌入多个用户水印,并要能够进行独立认证等要求,文章提出了一种基于CD-MA和HVS的多用户数字水印算法。该算法在用户水印嵌入之前,引入人类视觉系统模型,利用CDMA自身的扩频作用来提高水印的鲁棒性。仿真实验结果表明该算法能有效解决单水印数据嵌入量少、多用户水印存在水印碰撞、水印叠加嵌入相互影响、用户数量增加时水印作品质量严重下降等问题。     

HVS：一种基于实景图象的虚拟现实系统

大多数的虚拟现实比试在于计算机图形技术,先由多边形构造虚拟场景的三维几何模型,再由计算机根据用户的观察点和观察方向实时绘制出用户所看到的虚拟场景,ＨＶＳ 另一种思路,由计算机自动拉接、变形与组织许多幅度散的实景图象或连续视频,生成虚拟场景,这种虚拟场人有照片质量的视觉效果,被我们称为虚拟实景空间,虚拟实时空间能为用户提供、后退、仰视、俯视、３６０度环境、近看、远看等漫游能力,运行它不需要高性能的图