一种基于网格参数化的图像适应方法

图像适应是指将高分辨率的数字图像显示在手机、PDA等屏幕较小的显示终端上的过程.提出一种全新的基于网格参数化的图像适应方法,该方法的关键在于把图像表示为特征网格,从而将图像适应问题转化为网格的参数化,即求取一个与该特征网格同拓扑,且具有目标屏幕尺寸的网格.为了突出图像中的重要物体,该方法建立了源图像对应的特征网格与图像显著度的关系;通过优化基于显著度伸长的网格参数化的能量来求解适应图像的网格;然后借助纹理映射生成适应图像.另外,该方法在参数化的过程中增加了对显著区域和背景结构的约束,能够在保持并增强图像中重要物体的同时,使适应图像的结构不发生明显形变.该方法能够方便地处理具有复杂背景和包含多目标物体的图像的适应问题.实验结果显示了该方法的有效性.     

一种基于网格变形的图像放缩方法

基于内容的图像放缩的关键是如何保持图像中重要的内容,同时最小化整幅图像的视觉变形.文中将图像放缩问题转化成网格变形问题,提出一种改进的基于内容的图像放缩方法.首先在网格上建立保持整体形状的能量函数,结合约束条件,通过求解凸二次规划问题得到变形后的网格坐标,最终实现图像的放缩.实验结果表明,该方法不仅能够保持图像中重要的内容和特征结构,而且较好地保持了图像的整体性,使得图像视觉变形较小.     

骨架引导的网格模型圆柱面参数化

针对传统平面参数化不能直接对零亏格封闭模型参数化,而球面参数化较为适用于形态接近于球体模型的问题,定义了一种超圆柱面的参数域表示,并提出一种渐进的超柱面参数化算法,对于形态接近于圆柱或具有单支简单骨架的网格模型能够提供较小的几何形变;基于此,提出一种骨架引导的网格模型圆柱面参数化方法,能够对具有复杂骨架结构的网格模型实现全局参数化,它通过分块参数化由骨架信息得到的网格模型主体和分支,进而将分支圆柱面参数网格配准、优化并拼接至主体参数网格得到无缝的全局参数网格;对于人体和动物等具有明显骨架结构的网格模型,骨架引导的圆柱面参数化具有较小的几何形变.最后给出了实验结果,并展示了圆柱面参数化在约束纹理贴图中的应用.     

Image Retargeting Quality Assessment

Content‐aware image retargeting is a technique that can flexibly display images with different aspect ratios and simultaneously preserve salient regions in images. Recently many image retargeting techniques have been proposed. To compare image quality by different retargeting methods fast and reliably, an objective metric simulating the human vision system (HVS) is presented in this paper. Different from traditional objective assessment methods that work in bottom‐up manner (i.e., assembling pixel‐level features in a local‐to‐global way), in this paper we propose to use a reverse order (top‐down manner) that organizes image features from global to local viewpoints, leading to a new objective assessment metric for retargeted images. A scale‐space matching method is designed to facilitate extraction of global geometric structures from retargeted images. By traversing the scale space from coarse to fine levels, local pixel correspondence is also established. The objective assessment metric is then based on both global geometric structures and local pixel correspondence. To evaluate color images, CIE L*a*b* color space is utilized. Experimental results are obtained to measure the performance of objective assessments with the proposed metric. The results show good consistency between the proposed objective metric and subjective assessment by human observers.     

Mesh Parametrization Driven by Unit Normal Flow

Based on mesh deformation, we present a unified mesh parametrization algorithm for both planar and spherical domains. Our approach can produce intermediate frames from the original meshes to the targets. We derive and define a novel geometric flow: ‘unit normal flow (UNF)’ and prove that if UNF converges, it will deform a surface to a constant mean curvature (CMC) surface, such as planes and spheres. Our method works by deforming meshes of disk topology to planes, and spherical meshes to spheres. Our algorithm is robust, efficient, simple to implement. To demonstrate the robustness and effectiveness of our method, we apply it to hundreds of models of varying complexities. Our experiments show that our algorithm can be a competing alternative approach to other state-of-the-art mesh parametrization methods. The unit normal flow also suggests a potential direction for creating CMC surfaces.     

内容感知的图像重定向方法综述

随着各种智能设备的不断涌现,同一图像往往需要改变纵横比和大小来适应不同显示屏幕.基于内容感知的图像重定向方法通过研究图像重要内容的保持,使得图像自动适应到不同大小的显示设备上.主要对近年来基于内容感知的图像重定向方法的研究现状进行总结.按照重要度图的获取以及基于重要度图的重定向方法两方面回顾了手工特征的图像重定向;从基...     

基于灰度分布的图像三角网格化算法

借助于小波图像分解,提出一种基于图像内容的三角网格表示方法——基于双向模板的图像三角网格化算法.算法考虑图像的灰度分布,利用小波的图像分解能够将图像的各个方向的细节表现出来这一特性,给出符合原始图像灰度分布的三角划分,再对图像的三角划分进行三角网格化,最后获取整幅图像的网格划分.为了得到更好的重建图像质量,对该初始网格进行了细分,并针对三角网格规模的减小做出优化算法.同时提出一种记录模板号和细分点的数据存储结构,用二进制数据流来存储三角网格.通过实验数据对比,该算法能够很好的表示图像,在三角网格规模以及重建图像质量上较其它算法都有一定的优势,是一种极其有效的图像表示方法.     

基于区域关系图的图像显示适配技术

图像显示适配技术用于改编图像,以适应在不同尺寸和长宽比的目标屏幕上展示.其中,面向移动设备的图像显示适配面临展示面积受限、长宽比不固定等问题,已经成为多媒体领域的研究热点之一.针对现有方法的缺陷,提出了一种基于区域关系图的图像显示适配方法.首先,根据视觉关注程度和加权梯度分别计算出图像的重要度能量模板和敏感度能量模板.然后,将原始图像分解为曲边梯形网格,并进一步表示为区域关系图.在区域关系图基础上,图像显示适配被规约为用能量模板约束的二次规划问题,通过优化关键网格顶点重定位来生成重要物体突出且视觉扭曲不明     

Example‐Based Retargeting of Human Motion to Arbitrary Mesh Models

We present a novel method for retargeting human motion to arbitrary 3D mesh models with as little user interaction as possible. Traditional motion‐retargeting systems try to preserve the original motion, while satisfying several motion constraints. Our method uses a few pose‐to‐pose examples provided by the user to extract the desired semantics behind the retargeting process while not limiting the transfer to being only literal. Thus, mesh models with different structures and/or motion semantics from humanoid skeletons become possible targets. Also considering the fact that most publicly available mesh models lack additional structure (e.g. skeleton), our method dispenses with the need for such a structure by means of a built‐in surface‐based deformation system. As deformation for animation purposes may require non‐rigid behaviour, we augment existing rigid deformation approaches to provide volume‐preserving and squash‐and‐stretch deformations. We demonstrate our approach on well‐known mesh models along with several publicly available motion‐capture sequences.     

Aura Mesh: Motion Retargeting to Preserve the Spatial Relationships between Skinned Characters

Applying motion‐capture data to multi‐person interaction between virtual characters is challenging because one needs to preserve the interaction semantics while also satisfying the general requirements of motion retargeting, such as preventing penetration and preserving naturalness. An efficient means of representing interaction semantics is by defining the spatial relationships between the body parts of characters. However, existing methods consider only the character skeleton and thus are not suitable for capturing skin‐level spatial relationships. This paper proposes a novel method for retargeting interaction motions with respect to character skins. Specifically, we introduce the aura mesh, which is a volumetric mesh that surrounds a character's skin. The spatial relationships between two characters are computed from the overlap of the skin mesh of one character and the aura mesh of the other, and then the interaction motion retargeting is achieved by preserving the spatial relationships as much as possible while satisfying other constraints. We show the effectiveness of our method through a number of experiments.     

Random Accessible Mesh Compression Using Mesh Chartification

Previous mesh compression techniques provide decent properties such as high compression ratio, progressive decoding, and out-of-core processing. However, only a few of them supports the random accessibility in decoding, which enables the details of any specific part to be available without decoding other parts. This paper proposes an effective framework for the random accessibility of mesh compression. The key component of the framework is a wire-net mesh constructed from a chartification of the given mesh. Charts are compressed separately for random access to mesh parts and a wire-net mesh provides an indexing and stitching structure for the compressed charts. Experimental results show that random accessibility can be achieved with competent compression ratio, which is only a little worse than single-rate and comparable to progressive encoding. To demonstrate the merits of the framework, we apply it to process huge meshes in an out-of-core manner, such as out-of-core rendering and out-of-core editing.     

图像漫游：双灭点的松弛蜘蛛网格算法

为了解决蜘蛛网格算法在图像漫游中局限性，提出了双灭点的松弛蜘蛛网格算法。该算法在用于图像实时漫游时，用双灭点进行计算，其与前人提出的方法相比，更具通用性，不仅可以解决单灭点、双灭点、多灭点和灭线等不同类型的照片漫游问题，而且减轻了用户交互的工作量。此外，为了进一步提高图像的绘制质量，以获得高质量的漫游效果，还采用了一种分片绘制的策略。多种类型的图片实验证明了该算法的有效性。     

Parametrization of the Input-Output Image of Nonlinear Dynamic Systems

For dynamic systems described by differential equations with smooth functions in the state space, the size of the parameter space is minimized such that the input-output image of the system is preserved by finding the complete set of algebraic invariants for a fixed structure of the equations of the system. A relationship between the constructs of the algebra of functions used in the problem and the mathematical constructs used in the differential geometric approach is established. A method for finding the algebraic invariants—the analogs of Markov parameters of linear systems—is described.__________Translated from Avtomatika i Telemekhanika, No. 8, 2005, pp. 173–183.Original Russian Text Copyright © 2005 by Shumskii.This work was supported by the Russian Foundation for Basic Research, project no. 03-01-00791.     

Using an Intermediate Skeleton and Inverse Kinematics for Motion Retargeting

In this paper, we present a new method for solving the Motion Retargeting Problem, by using an intermediate skeleton. This allows us to convert movements between hierarchically and geometrically different characters. An Inverse Kinematics engine is then used to enforce Cartesian constraints while staying as close as possible to the captured motion.     

基于网格优化的图像纹理替换方法

提出一种新的图像纹理替换方法,该方法在原始图像精确几何及光照信息未知的情况下,用新的纹理有效替换原始图像目标区域的纹理并逼真地保持了原始纹理的扭曲变形和光照效果.该方法借助反求的法向信息,通过一种基于网格边长伸展的参数化方法优化求得原始图像目标区域上划分的网格在纹理空间中的对应网格,有效模拟了原始纹理由于隐藏几何和透视投影引起的纹理扭曲效果;进而通过YCbCr颜色空间转换和传递保持了原始纹理的光照阴影效果.由于求取纹理采样规则的优化方法仅仅与原始图像空间相关,而与替换纹理无关,因而对目标图像处理一次后,可以有效地应用于任意新纹理的替换.通过适当的交互,替换纹理的纹元尺度渐变及纹理自遮挡效果亦可有效模拟.实验展示了良好的纹理替换效果.     

Image Processing to Automate Mesh Generation

Finite element modeling is now a standard approach used in the industry to minimize costly trials and help reduce the overall lead time in product and process design. However, building surface/solid models defining the product shape and generating finite element meshes for analyses still require a significant amount of the engineers’ time. In this paper, we present a new method for automatically generating a finite element mesh directly from bitmap images obtained from an artist’s concept of a label for an embossed aluminum beverage can, and demonstrate its application towards the building of tooling mesh models used in the modeling of the embossing process. This approach completely eliminates the need for creating a surface/solid model, thus resulting in a dramatic reduction in the time required for process design.     

一种人体运动重定向方法*

提出人体下肢向量的概念,通过分析人体运动指出下肢向量能保持运动的主要特征,由此提出基于下肢向量特征不变性的人体运动重定向方法,以此提高运动捕获数据的可重用性。该方法面向人体下肢的运动重定向,能够将运动数据从原始骨骼模型重定向到具有不同骨骼长度比例的目标骨骼模型,同时保持原始运动的主要特征。实验结果表明,该方法具有较好的运动重定向效果和较快的计算效率。     

网格缩减的自适应hp伪谱法

针对控制变量不连续的最优控制问题,本文提出一种自适应更新的忉伪谱法,这种方法在(Legendre Gauss Radau,LGR)点处取配点,能够以较小的网格规模获得较高的精度.通过计算相对误差估计,判断网格规模是增加还是缩减,若相对容许误差大于给定值,则增加网格区间数或网格配点数提高解的精度,反之则合并网格或减小网格配点数缩减网格规模提高计算效率.将hp伪谱法应用于最优控制问题,仿真验证了hp伪谱法的优越性.     

Stellar Mesh Simplification Using Probabilistic Optimization

This paper proposes the stellar mesh simplification method, a fast implementation of the Four‐Face Cluster (FFC) algorithm. In this method, a probabilistic optimization heuristic substitutes the priority queue of the original method, which results in a 40% faster algorithm with the same order of distortion. It extends naturally to a progressive and/or multiresolution scheme for combinatorial surfaces. This work also presents a simple way to encode the hierarchy of the resulting multiresolution meshes. This work also focuses on important aspects for the development of a practical and robust implementation of this simplification technique, and on the analysis of the influence of the parameters.