一种基于自适应闭值的图像伪造检测算法

图像伪造检测是数字取证领域一个发展迅速的研究方向。复制一移动是最常见的图像伪造方式之一,其目的是通过隐藏或克隆对象来创建新的图像内容场景。复制一移动伪造检测的主要依据是图像中存在较大面积的相同或非常相似的区域对。针对以往检测方法对图像中存在同质纹理或均匀区域检测困难以及相关参数阂值选择不确定等现状,提出一种基于自适应阂值的图像复制一移动伪造检测算法,该算法不但使相关阂值的选择和估计更合理,而且能够自动识别和定位伪造区域。通过在包含同质或均匀区域的彩色伪造图像中的实验,进一步验证了本算法的有效性。     

利用三维自适应分裂-合并的MRI图像分割算法设计

为了在医学图像分割中,发现均匀几何三维区域的复杂形状,以提高分割准确率,提出一种基于3D几何特征分裂-合并(ASM)的脑部MRI图像分割算法;首先构建简单平行六面体的12种3D区域分割策略,体积分割技术将整个体积划分为许多大的均匀三维几何区;然后,在体积内定义更多小的均匀区域,以便在随后的合并步骤中有更大的生存概率;最后,进行多级区域合并,合并阶段只涉及复杂ASM树的叶子,考虑灰度相似性和共同边界区的大小,将小的区域合并为大邻近区;相比其他几种MRI图像分割算法,提出的方法在分割过程对噪声具有鲁棒性,提高了分割性能和准确率;另外提出的方法不需要训练数据集。     

An adaptive window mechanism for image smoothing

Image smoothing using adaptive windows whose shapes, sizes, and orientations vary with image structure is described. Window size is increased with decreasing gradient magnitude, and window shape and orientation are adjusted in such a way as to smooth most in the direction of least gradient. Rather than performing smoothing isotropically, smoothing is performed in preferred orientations to preserve region boundaries while reducing random noise within regions. Also, instead of performing smoothing uniformly, smoothing is performed more in homogeneous areas than in detailed areas. The proposed adaptive window mechanism is tested in the context of median, mean, and Gaussian filtering, and experimental results are presented using synthetic and real images and compared with a state-of-the-art method.     

Segmentation of remotely-sensed images by a split-and-merge process+

Abstract

This paper describes the application of an image segmentation technique to remotely-sensed terrain images used for environmental monitoring. The segmentation is a preprocessing operation which is applied prior to image classification in order to improve classification accuracy from that achievable by classifying pixels individually on the basis of their spectral signatures. The method uses a split-and-merge technique to segment images into regions of homogeneous tone and texture wherever this is possible. The split-and-merge technique employs a hierarchical quadtree data structure. Texture is measured using easily computed grey value difference statistics. The homogeneity criteria employed in region merging are dependent on local statistics. The segmented image is classified using a region classifier for regions and the normal per-pixel classifier for single pixels in areas of inhomogeneity. The technique is illustrated by example classifications of aerial Multispectral Scanner data from two test sites. A quantitative analysis of the performance shows that an increased classification accuracy is achieved.     

各向同性同质区域选取的高光谱遥感图像噪声估计方法

在现有高光谱遥感图像噪声估计方法中,同质区域的选取通常是最关键的步骤,有效的同质区域选取方法能够提高图像的噪声估计精度。本文充分利用了高光谱遥感图像中丰富的空间信息和光谱信息,提出了一种各向同性同质区域选取算法,其中,为了更好地区分同质区域内像元相似度,构造了一种新的兰氏-光谱角度量;结合基于多元线性回归的去相关法,通过最优区域评估高光谱遥感图像噪声水平。利用不同结构及信噪比的模拟图像和真实高光谱遥感图像进行实验,通过与现有的多种噪声估计方法比较,验证了本文方法在针对不同噪声水平、不同复杂程度的图像时更加准确和稳定。     

基于噪声方差估计的伪造图像盲检测方法

针对不同来源合成伪造数字图像提出了一种盲检测方法,不同数字图像背景噪声存在差异,因而伪造图像区域噪声方差不同。从待测图像小波分解后的高频子带中去除相应边缘区域的高频干扰,改进了噪声方差估计算法,并对所得噪声图像进行分块处理估计每一个分块的噪声方差,将方差相近的块进行融合,最后比较图像中纹理接近的同质区域,找出方差异常的位置。通过实验研究了方差估计精度,对不同来源的伪造图像进行了检测,结果表明算法提高了图像噪声方差的估计精度,在图像纹理接近的同质区域中可以定位图像的伪造区域。     

Image‐object detectable in multiscale analysis on high‐resolution remotely sensed imagery

Landscapes are complex systems composed of a large number of heterogeneous components as well as explicit homogeneous regions that have similar spectral character on high‐resolution remote sensing imagery. The multiscale analysis method is considered an effective way to study the remotely sensed images of complex landscape systems. However, there remain some difficulties in identifying perfect image‐objects that tally with the actual ground‐object figures from their hierarchical presentation results. Therefore, to overcome the shortcomings in applications of multiresolution segmentation, some concepts and a four‐step approach are introduced for homogeneous image‐object detection. The spectral mean distance and standard deviation of neighbouring object candidates are used to distinguish between two adjacent candidates in one segmentation. The distinguishing value is used in composing the distinctive feature curve (DFC) with object candidate evolution in a multiresolution segmentation procedure. The scale order of pixels is built up by calculating a series of conditional relative extrema of each curve based on the class separability measure. This is helpful in determining the various optimal scales for diverse ground‐objects in image segmentation and the potential meaningful image‐objects fitting the intrinsic scale of the dominant landscape objects. Finally, the feasibility is analysed on the assumption that the homogeneous regions obey a Gaussian distribution. Satisfactory results were obtained in applications to high‐resolution remote sensing imageries of anthropo‐directed areas.     

融合颜色和深度信息的图像物体分割算法*

当图像中存在阴影、低对比度边缘和模糊区域时,传统算法仅利用外观信息难以准确提取物体轮廓,而深度不连续性为辨识物体边界提供有用信息。文中提出基于颜色和深度信息的图像物体分割算法,首先利用mean-shift算法对图像进行适度的过分割,然后融合颜色和深度信息充分描述过分割区域的特性,根据深度信息自动选取目标和背景的种子区域,最后基于最大相似度进行区域合并,得到图像物体分割结果。在Middlebury和NYU-V2数据库上的实验表明,相比当前通用算法,文中算法简单有效,能提高分割的准确性,改善分割图像的视觉效果。     

Image segmentation with directed trees

This correspondence presents a simple algorithm to detect and label homogeneous areas in an image, using directed trees for region labeling. The scheme constructs directed trees with the image points as nodes, guided by an edge value computed at every point. These directed trees segment the image into disjoint regions. Because of a valley seeldng property of the tree construction procedure, the boundaries separating the resultant segments pass through the center of the edges. The algorithm thus performs wel1 with thick and wide edges of varying height, because no thresholding of the edge image is involved. The properties of the resultant segments are stated in terms of the edge image. The algorithm is shown to be simple, efficient, and effective for detecting homogeneous segments in the presence of noise. Results of application in the algorithm to segment a LANDSAT multispectral scene of an agricultural area are included.     

一种基于局部方向尺度的各向异性扩散图像滤波方法

针对图像滤波去噪模糊边缘结构的弊端,提出了一种基于局部方向尺度的各向异性扩散图像滤波方法。该方法首先为图像中每个象素定义相应的局部方向尺度,然后利用象素的局部方向尺度在边缘附近或细小结构的小区域内进行小尺度扩散滤波,而在较大的均匀区域的内部则进行大尺度扩散滤波。实验结果表明算法比现存的各向异性扩散滤波方法在保持图像的细小结构和对象边缘方面具有更好的性能。     

Text region extraction in a document image based on the Delaunay tessellation

In this paper, Delaunay triangulation is applied for the extraction of text areas in a document image. By representing the location of connected components in a document image with their centroids, the page structure is described as a set of points in two-dimensional space. When imposing Delaunay triangulation on these points, the text regions in the Delaunay triangulation will have distinguishing triangular features from image and drawing regions. For analysis, the Delaunay triangles are divided into four classes. The study reveals that specific triangles in text areas can be clustered together and identified as text body. Using this method, text regions in a document image containing fragments can also be recognized accurately. Experiments show the method is also very efficient.     

非参数化区域竞争方法:一种新的图像分割框架

提出了一种新的图像分割框架--非参数化区域竞争算法.这种算法克服了基于尺度 空间滤波的特征空间聚类法的缺陷,提高了原区域竞争算法的性能,并且采取了一种自动选取 种子位置及大小的形式化策略.非参数化区域竞争算法可以把图像分割成统计意义上并不具有 一致性,但在应用中更有意义的区域,称这样的分割为语义一致(或均匀)的分割.非参数化区域 竞争算法把定量地控制分割结果中的区域个数和语义一致的分割结合起来,从而净化了分割结 果,并且可以降低后继算法的复杂度.     

融合模糊Histon阈值和FCM的Lab空间色彩分割算法

提出了一种简单有效的自适应无监督方法。在CIELab空间中利用模糊Histon阈值技术获得图像中所有可能的均匀区域,即通过寻找峰值,区域初始分割和区域颜色相似性合并,获得由聚类中心标注的均匀区域,提出自适应FCM聚类算法以提高均匀区域之间的紧密度,最终完成色彩分割。该算法已成功应用到伯克利图像库,相比当前一些无监督色彩分割算法,例如：Mean-Shift、NCuts取得了合理更好的划分,视觉上有效提取目标物体,具有一定鲁棒性。     

Image data field for homogeneous region based segmentation

Some innovative methods for image segmentation inspired by physical world are presented in recent years. Aiming to find homogeneous regions and latent semantic information, the paper presents a novel image segmentation method based on image data field. Image data field, developed by simulating the short-range nuclear forces field theory in the physical world, can effectively represent the spatial interactions of neighborhood pixels. Then, the homogeneous regions are characterized by maximum tolerance classes, which induced by homogeneous attraction relation comparing the contributions of potential values in image data field. More specifically, the proposed method mainly focuses on the images with uneven lighting conditions. Compared with the existing relative methods on a variety of images, the experimental results suggest that the presented method is efficient and effective.     

基于同构RBF网络的视差图像分治重建

提出一种基于同构径向基函数(RBF)网络的视差图像分治重建方法,通过可调域值和边缘检测完成视差图像的区域分割,在每个区域内采用RBF神经网络进行重建,将各个区域进行拼接,得到最终的重建结果。在不同区域运用RBF进行重建时根据各区域结构特征的繁简用不同分辨率的数据进行训练。实验结果表明,该方法可以获得高质量的重建结果。     

基于内容的网格生成算法

在基于模型的编码技术中,选择合适的网络模型对提高模糊的运动估计精度、编码效率和得到高质量的解码图像都是至关重要的。本文提出的基于图像内容的自适应网络模型生成算法,首先利用数学形态学中的水线算法把编码图像分割成许多纹理一致的区域,所分割的区域反映了图像的结构、轮廓和边界;再对这些区域的边界进行多边形拟合,得到多边形各个边的端点作为网格模型的节点,以这些节点为基础就能生成一个Ｄｅｌａｕｎａｙ三角形网格     

A feature-oriented forward–backward diffusion model for intensity image restoration based on level set motion

In this paper, a new enhancing and smoothing partial differential equation coupled with time-delay regularization is presented, which is based on local geometric properties desired for image restoration. To reverse the process of image deterioration, a newly defined shock filter for edge enhancing is combined with a level set motion-based regularization equation. The balance between the backward process and the forward process is carried out by a weighting function coupled with time-delay regularization helping to identify boundary areas and homogeneous regions in a given image. The proposed model is well-posed in terms of viscosity solutions – the existence and uniqueness of periodic viscosity solution to the initial value problem of the equation is established. Numerical results for some kinds of grey-level images are demonstrated to confirm our anticipation.     

融合上下文信息的场景结构恢复

提出了一种融合场景上下文信息的两级分类算法,从单幅图像中恢复场景结构。室外场景的结构化特征使其3维结构可以粗略地分为3类:"地面","天空"以及"竖直物体"。首先,把图像分割成具有灰度和颜色一致性的区域;其次确定特征显著区域("确定区域")的结构,将特征不明显的区域标记为"未知区域";然后根据"未知区域"与"确定区域"的相似性及"确定区域"场景结构对"未知区域"的可能结构进行投票,将投票最多的结构类型赋予"未知区域";最后介绍场景结构恢复在构造场景3维模型方面的应用。实验结果表明,由于利用了场景结构的上下文信息,该算法场景结构恢复的正确率为92.3%,优于现有算法88.1%的恢复正确率。     

Locally adaptive linear mixture model-based super-resolution land-cover mapping based on a structure tensor

Super-resolution land-cover mapping (SRM) is a technique for generating land-cover thematic maps with a finer spatial resolution than the input image. Linear mixture model-based SRM (LSRM) is applied directly to a remotely sensed image and is composed of a spatial term that integrates the land-cover spatial pattern prior information, a spectral term that assumes that the spectral signature of each mixed pixel is composed of a weighted linear sum of endmember spectral signatures within that pixel and a balance parameter that defines the weight of the spatial term. The traditional LSRM adopts an isotropic spatial autocorrelation model in the land-cover spatial term for different classes and a fixed balance parameter for the entire image, and ignores the image local properties. The class boundaries are at risk of oversmoothing and may be imprecise, and the homogeneous regions may be unsmoothed and contain speckle-like artefacts in the result. This study proposes a locally adaptive LSRM (LA-LSRM) that integrates image local properties to predict fine spatial resolution pixel labels. The structure tensor is applied to detect the image local information. The LA-LSRM spatial term is locally adaptive and is composed of an anisotropic spatial autocorrelation model in which the spatial autocorrelation orientations of different classes may vary. The LA-LSRM balance parameter is locally adaptive to the different regions of the image. Such parameter obtains a relatively large value when the fine-resolution pixel is located in the homogeneous region to remove speckle-like artefacts and a relatively small value when the fine-resolution pixel is at the class boundary to preserve the edge. The LA-LSRM performance was assessed using a simulated multi-spectral image, an IKONOS multi-spectral image, a hyperspectral image produced by Airborne Visible/Infrared Imaging Spectrometer and a hyperspectral image produced by reflective optics system imaging spectrometer. Results show that the homogeneous regions were smoothed, the boundaries were better preserved and the overall accuracies were increased by LA-LSRM compared with traditional LSRM in all experiments.     

Spatial variability of air temperature and appropriate resolution for satellite‐derived air temperature estimation

This study investigates the spatial variability of air temperature over Hong Kong using in situ air temperature recorded from a mobile traverse combined with an ASTER thermal satellite image. Three different degrees of urbanization in Hong Kong, including city downtown (Kowloon), suburban areas (Yuen Long and Shatin), and rural countryside (Tai Mo Shan and Lam Tsuen) are analysed. The spatially variable relationship between air and surface temperature was evaluated using two spatial averaging techniques, namely spatial resampling and buffering around air temperature points. The strength of the correlation coefficient was tested for every decreasing resolution and the appropriate spatial scales of air temperature in urban, suburban and rural areas were found to be 200 m, 450 m and 700 m, respectively. The differences in the spatial scales of air temperature in these regions are attributed mainly to structural factors of land cover such as city block size, building density and percentage of green areas, and secondarily to the climatic conditions being operating in, and which commonly typify these individual regions. Thus small scale lengths in the urban area corresponded to heterogeneous land cover, a well developed urban boundary layer, low wind speeds and a low lapse rate, whereas longer scale lengths were observed in suburban and rural areas having more homogeneous land cover, higher wind speeds and higher lapse rate.