Merging radiometric grids using histogram matching

Large-scale compilations of airborne geophysical data are an important part of regional-scale mineral exploration and in most cases, the compilation involves merging datasets of varying quality, acquired over a long period of time. Merging radiometric datasets involves the additional complication that many older surveys were flown with uncalibrated spectrometer systems. Conventional grid merging is based on calculation of base-level shift and scaling factors for each grid with the grid edges feathered. However, even after these corrections, soil moisture differences between surveys acquired over a long period of time and at different seasons when soil moisture content varied introduce scaling errors into the estimated radioelement concentrations. An alternative method based on histogram matching is suggested as an improvement on existing methods. Source code in Matlab format is available from the server at www.iamg.org.     

Scale-invariant template matching using histogram of dominant gradients

This paper presents a histogram-based template matching method that copes with the large scale difference between target and template images. Most of the previous template matching methods are sensitive to the scale difference between target and template images because the features extracted from the images are changed according to the scale of the images. To overcome this limitation, we introduce the concept of dominant gradients and describe an image as the feature that is tolerant to scale changes. To this end, we first extract the dominant gradients of a template image and represent the template image as the grids of histograms of the dominant gradients. Then, the arbitrary regions of a target image with various locations and scales are matched with the template image via histogram matching. Experimental results show that the proposed method is more robust to scale difference than previous template matching techniques.     

基于投影直方图匹配的双目视觉跟踪算法

为了在机器人机械手双目视觉伺服系统中跟踪并精确定位目标的空间位置,提出了一种利用投影直方图匹配和极线几何约束的目标跟踪方法。分别在2个视觉中人工标定目标,并提取目标在多颜色空间的水平、垂直投影直方图作为匹配模板;在一个视觉中利用目标的运动一致性原则和投影直方图匹配搜索并跟踪目标;在另一个视觉中依据双目视觉系统的极线几何原理限定目标搜索范围,搜索并定位目标。该方法利用水平、垂直投影直方图描述目标的结构信息,同时完成了双目视觉系统中的目标跟踪与配准功能,有利于目标的精确定位和视觉测量。实验结果表明,该方法可在双目视觉系统中有效跟踪目标,运算效率高,鲁棒性强。     

Uniform texture synthesis and texture mapping using global parameterization

Texture mapping and texture synthesis are two popular methods for the decoration of surfaces with visual detail. Here, an existing challenge is to preserve, or at least balance, two competing metrics: scale and angle. In this paper we present two methods for this, both based on global conformal parameterization. First, we describe a texture synthesis algorithm for surfaces with arbitrary topology. By using the conformal parameterization, the 3D surface texture synthesis problem can be converted to a 2D image synthesis problem, which is more intuitive, easier, and conceptually simpler. While the conformality of the parameterization naturally preserves the angles of the texture, in this paper we provide a multi-scale technique to also maintain a more uniform area scaling factor. A second novel contribution is to employ the global parameterization to simultaneously preserve orthogonality and size in texture mapping. For this, we show that a conformal factor-driven mass-spring method offers a convenient way to trade off these two qualitative metrics. Our algorithms are simple, efficient and automatic, and they are theoretically sound and universal to general surfaces as well.     

Generating haptic texture using solid noise

Texture enhances haptic interaction by providing unique, distinguishable, and versatile surfaces. In computer haptics, texture can render environments more realistic and provide useful information. In this paper, an algorithm is proposed for virtual texture simulation by using solid noise, where only a few parameters need to be altered to generate a range of realistic and diverse textures by reproducing different frequencies similar to that of real vibrational signals in a virtual environment. The proposed method can capture the textural effect in a haptic simulation while retaining a simple overall geometry and stable update rate. This method also allows the user to change the texture at runtime and can be easily incorporated into any existing code and used in any traditional haptic device without affecting overall haptic-rendering performance. Moreover, the solid noise texture is independent of object geometry and can be applied to any shape without additional computations. We conducted a human-subject study to evaluate the recognition accuracy for each generated haptic texture as well as its realism and correspondence to real texture. The results indicated the high performance of the method and its ability to generate haptic textures with a very high recognition rate that were highly realistic.     

Automated eye motion using texture synthesis

Modeling human eyes requires special care. The goal of this paper is to synthesize realistic eye-gaze and blink motion, accounting for any possible correlations between the two. The technique adopts a data-driven texture synthesis approach to the problem of synthesizing realistic eye motion. The basic assumption is that eye gaze probably has some connection with eyelid motion, as well as with head motion and speech. But the connection is not strictly deterministic and would be difficult to characterize explicitly. A major advantage of the data-driven approach is that the investigator does not need to determine whether these apparent correlations actually exist. If the correlations occur in the data, the synthesis (properly applied) will reproduce them.     

空间各向异性肝动脉体纹理合成方法研究

针对空间上具有各向异性的体纹理,提出一种基于样本的体纹理合成方法,把二维情况下基于二维纹理样本块的粘贴技术扩展至三维,应用到构建好的肝动脉模型。根据用户在四面体网格上定义的张量场,以四面体为合成单元,粘贴各向异性的三维纹理样本块。实验结果与理论分析表明,该方法可以在任意三维区域根据用户的交互合成预期的纹理效果,且能够较好地模拟肝动脉的内部结构,实现切割的实时可视化。     

螺旋线状搜索的快速块匹配纹理合成

为了避免纹理映射技术可能带来接缝走样的缺陷和过程纹理合成中复杂参数的调试,采用基于样图的纹理合成方法提出了一种新算法.该算法基于纹理的连贯性,在采用徐晓刚螺旋线状搜索算法的同时,结合了梁林的块拼贴纹理合成算法,即利用连贯性在样图中已合成纹理块位置向邻域扩展进行螺旋搜索,直到搜索到最佳匹配纹理块,然后进行纹理合成.大量实验结果表明,该算法与上述两种算法相比在合成效果上更加理想,合成时间也大大提高.     

High efficiency and quality: large graphs matching

Graph matching plays an essential role in many real applications. In this paper, we study how to match two large graphs by maximizing the number of matched edges, which is known as maximum common subgraph matching and is NP-hard. To find exact matching, it cannot a graph with more than 30 nodes. To find an approximate matching, the quality can be very poor. We propose a novel two-step approach that can efficiently match two large graphs over thousands of nodes with high matching quality. In the first step, we propose an anchor-selection/expansion approach to compute a good initial matching. In the second step, we propose a new approach to refine the initial matching. We give the optimality of our refinement and discuss how to randomly refine the matching with different combinations. We further show how to extend our solution to handle labeled graphs. We conducted extensive testing using real and synthetic datasets and report our findings in this paper.     

基于空间纹理相似性的图像角点特征匹配算法

本文针对传统图像角点特征匹配算法的匹配速度慢且准确率低等问题,提出一种基于空间纹理相似性的图像角点特征匹配算法。首先,计算图像目标上角点对应的空间距离矩阵;然后,通过计算图像角点的空间距离矩阵在对应角点邻域LBP特征向量上的瑞利商,将角点在图像灰度特征空间内的度量问题转换为纹理特征空间内幅值的度量问题;最后,根据角点对应的瑞利商的大小,实现不同图像间的角点特征匹配。对不同条件下采集的图像进行角点特征匹配,得到的匹配结果表明本文算法不仅能够很好的适应图像光照、几何变化,得到的匹配正确率较高,同时与传统算法相比本文算法在运行时间上也有大幅度的降低,当处理特征数量较小时平均降低48ms,而匹配特征数量较多时能够降低2408ms。     

Texture mixing and texture movie synthesis using statisticallearning

We present an algorithm based on statistical learning for synthesizing static and time-varying textures matching the appearance of an input texture. Our algorithm is general and automatic and it works well on various types of textures, including 1D sound textures, 2D texture images, and 3D texture movies. The same method is also used to generate 2D texture mixtures that simultaneously capture the appearance of a number of different input textures. In our approach, input textures are treated as sample signals generated by a stochastic process. We first construct a tree representing a hierarchical multiscale transform of the signal using wavelets. From this tree, new random trees are generated by learning and sampling the conditional probabilities of the paths in the original tree. Transformation of these random trees back into signals results in new random textures. In the case of 2D texture synthesis, our algorithm produces results that are generally as good as or better than those produced by previously described methods in this field. For texture mixtures, our results are better and more general than those produced by earlier methods. For texture movies, we present the first algorithm that is able to automatically generate movie clips of dynamic phenomena such as waterfalls, fire flames, a school of jellyfish, a crowd of people, etc. Our results indicate that the proposed technique is effective and robust     

Video texture modelling and synthesis using fractal processes

The authors propose a new approach for the synthesis of natural video textures using a fractal- based approach. Specifically, a video texture is modelled according to the three-dimensional (3D) extended self-similar (ESS) model introduced, which generalises the fractional Brownian motion process. The analysis of original video textures is based on the estimation of the autocorrelation functions (ACFs) of the textures' increments. The 3D-ESS model is then used to synthesise a process whose increments have the same ACFs of the given prototype. The synthesis is accomplished by generalising to the 3D case the incremental Fourier synthesis algorithm. Experimental results for the analysis and synthesis of natural video textures are eventually provided.     

Efficient texture synthesis using strict Wang Tiles

Wang Tiles are constructed from four texture samples, arranged so they can always match a choice of other tiles at two edges. Because they are precomputed, Wang Tiles are a very efficient way to generate textures on the fly. But matching problems occur within tiles and at the corners of adjacent tiles. By replacing the edge-matching texture samples with a new sample in the center of the tile, and using the graph cut path-finding algorithm, we overcome these problems and introduce additional texture diversity. Our s-Wang Tiles are a stricter interpretation of the original Wang Tile design, and our tile set is also smaller than that required by ω-Tiles: only eight different tiles are required for a non-repetitive titling.     

Facial image synthesis using skin texture recording

A significant issue in synthesizing realistic faces is the representation of skin grain and wrinkles. This paper describes a new approach based on the registered body of a real person. This recording allows simultaneously registering of the 3-D coordinates of a point and the corresponding reflected intensity. Using a 4-D B-spline surface to reconstruct the face, we come close to achieving a photographic result.     

Real-time structured texture synthesis and editing using image-mesh analogies

We present a novel texture synthesis technique designed to reproduce at real-time frame-rates example texture images, with a special focus on patterns characterized by structural arrangements. Unlike current pixel-, patch- or texton-based schemes, that operate in image space, our approach is structural. We propose to assimilate texture images to corresponding 2D geometric meshes (called texture meshes). Our analysis mainly consists in generating automatically these meshes, while synthesis is then based on the creation of new vertex/polygon distributions matching some arrangement map. The output texture image is obtained by rasterizing the previously generated polygons using graphics hardware capabilities, which guarantees high speed performance. By operating in geometry space instead of image/pixel space, the proposed structural approach has a major advantage over current techniques: beyond pure texture reproduction, it allows us to define various tools, which allow users to further modify locally or globally and in real-time structural components of textures. By controlling the arrangement map, users can substitute new meshes in order to completely modify the structural appearance of input textures, yet maintaining a certain visual resemblance with the initial example image.     

A fast,non-iterative and exact histogram matching algorithm

A fast, non-iterative algorithm is presented for transforming an image so as to give it exactly a given target histogram. This is achieved for any original and target histogram combinations and examples of results are given in addition to a comparison with applying the earth mover's distance (EMD) method to this task.     

基于骨架和统计直方图的形状匹配算法

目标的柔性变化和局部遮挡是形状匹配的主要困难,传统的形状匹配算法对这类问题常不能奏效。针对该问题,提出了一种新的接合骨架和统计直方图匹配柔性变化和局部遮挡目标的方法。算法首先提取骨架接合点,根据骨架接合点将目标形状分块;基于每个骨架接合点构造各个子块的不变特征并将其直方图化;再构建了一种新的相似性度量函数;通过对骨架接合点的匹配实现目标形状的匹配。由于算法是提取骨架接合点,较骨架端点提取更稳定,从而能提高匹配精度;此外算法采用分块描述匹配的思想,所以能有效处理局部遮挡和柔性变化。理论分析和实验结果均表明算法是有效的。     

Shapeme histogram projection and matching for partial object recognition

Histograms of shape signature or prototypical shapes, called shapemes, have been used effectively in previous work for 2D/3D shape matching and recognition. We extend the idea of shapeme histogram to recognize partially observed query objects from a database of complete model objects. We propose representing each model object as a collection of shapeme histograms and match the query histogram to this representation in two steps: 1) compute a constrained projection of the query histogram onto the subspace spanned by all the shapeme histograms of the model and 2) compute a match measure between the query histogram and the projection. The first step is formulated as a constrained optimization problem that is solved by a sampling algorithm. The second step is formulated under a Bayesian framework, where an implicit feature selection process is conducted to improve the discrimination capability of shapeme histograms. Results of matching partially viewed range objects with a 243 model database demonstrate better performance than the original shapeme histogram matching algorithm and other approaches.