一种手绘草图的快速参数化方法

本文提出了一种快速手绘草图参数化方法,该方法利用 Bézier 曲线拟合手绘草图,并依靠误差控制来逼近曲线,最大限度地保留了手绘草图的原始信息;同时,建立了手绘草图的统一的参数化模型。实验表明:该方法对各种图形都具有较好的拟合效果,并具有很高的时间效率。     

结合图元与感知哈希的手写输入简笔画识别

目的 为了克服手写输入中随意性强和自由度大的缺陷,同时兼顾简笔画的整体属性和局部特征,提出一种基于图元识别与感知哈希技术相结合的手写输入简笔画二级识别算法。方法 首先提取笔画的几何特征、笔序特征及结构特征且进行识别,然后查找由图元信息、笔画结构信息和笔序信息构成的简笔画语义库,完成由规则的几何图元构成的简笔画识别;若未被识别,则生成简笔画图像,利用感知哈希技术完成简笔画图像的识别。结果 基于本文提出的简笔画识别方法,实现了对样本库中150种简笔画对象的识别,平均识别率为82.6%。结论 实验结果表明,对于不同用户手写输入的任意样本库中的简笔画,该方法具有较高的识别率,此外,还可以通过在简笔画语义库和样本库中增加简笔画的种类等方式实现对更多种类简笔画的扩展识别。     

基于样本学习的人像线条画生成系统

介绍了一个基于样本学习的人脸线条画生成系统.该系统可以根据用户给定的正面人脸照片自动生成相应的人脸线条画.在系统中有两个关键技术,即非参数化采样方法和灵活的线条画模板.对于给定图像上的任意像素点及其邻域,通过在样本空间搜索并匹配所有的相似邻域,计算该像素点在相应的线条画上出现的条件概率;然后根据艺术家的风格和得到的条件概率绘制"期望的线条画";最后使用模板匹配得到最后的线条画.此方法可以生成高质量的正面人脸线条画.     

论设计素描对产品设计的促进作用

分别通过对产品设计及设计素描的涵义分析,说明了产品设计的基本原则与设计素描的特点及其所培养能力的相似性,指出设计素描作为产品设计基础训练的必要性,并通过具有想象与创意的素描训练,对产品设计起到促进的作用。     

结合pHash和稀疏编码的素描人脸合成方法

为解决已有素描人脸合成方法存在的细节模糊和清晰度低的问题,提出一种感知哈希算法（Perceptual Hash,pHash）与稀疏编码（Sparse Coding,SC）相结合的素描人脸合成方法。首先根据图像的信息熵对人脸照片-素描对进行自适应分块处理,利用感知哈希算法计算出大图像块的哈希指纹,并对小图像块进行稀疏编码;然后选取与测试照片块最相似的[K]个初始候选照片块,得到与之对应的素描块;最后引入二次稀疏编码方法,合成最终的素描块,进而合成整幅素描人脸图像。利用现有的人脸数据库验证了算法的有效性,该算法经优化后可用于素描人脸合成。     

异构CAD 数据交换中样条草图的处理方法

针对现有异构CAD 系统间的产品数据交换方法对样条草图处理不足问题,提出了 支持样条草图参数化交换的草图数据交换构架。将草图数据交换分为简单参数草图数据交换和 复杂参数草图数据交换。重点分析了复杂参数草图数据交换问题,通过引入Hausdorff 距离作 为适应度评价方法,构建了基于粒子群优化求解的样条草图参数化交换算法,利用曲率自适应 学习因子来避免局部最优解,使得不同曲率区域的参数点位置合理分布。所提方法在异构CAD 系统间进行了实验测试,结果证明了本方法的有效性。     

笔输入草图的分层识别

针对计算机支持的草图设计技术中的草图识别这个核心问题，给出了一套分步逐层的识别方案：从原始笔划的在线识别与线元转换，到几何层基于上下文的草图规整，到语义层基于领域知识的草图理解．整个识别过程通过一个带有黑板的知识库系统实现，逐步有效地解决了草图的模糊性与不确定性，将原始草图转换为精确的几何图形．文中方法已经过原型草图工具系统ISID的验证，并取得良好效果．     

Extracting a polyhedron from a single-view sketch: Topological construction of a wireframe sketch with minimal hidden elements

An essential prerequisite to construct a manifold trihedral polyhedron from a given natural (or partial-view) sketch is solution of the “wireframe sketch from a single natural sketch (WSS)” problem, which is the subject of this paper. Published solutions view WSS as an “image-processing”/“computer vision” problem where emphasis is placed on analyzing the given input (natural sketch) using various heuristics. This paper proposes a new WSS method based on robust tools from graph theory, solid modeling and Euclidean geometry. Focus is placed on producing a minimal wireframe sketch that corresponds to a topologically correct polyhedron.     

Modeling piecewise helix curves from 2D sketches

We describe a method for a reconstructing piecewise helix curve from its 2D sketch. The system takes as input a hand-drawn polygonal curve and generates a piecewise helix curve such that its orthogonal projection matches the input curve. The first step is an algorithm to generate a set of helices such that their orthogonal projection approximates the input curve. This step is followed by a global optimization to minimize the tangent discontinuity of the junctions of the helices while keeping the fitting error small.     

基于手势和草图的概念设计协同交互的研究

基于手势和草图的交互模式提供了一种自然和谐的方式来支持概念设计协同操作,促进协同工作系统的发展与应用．基于以用户为中心的设计,比较了不同方式的概念设计过程,提出了基于手势和草图的协同设计方法,进一步讨论了以草图为设计过程中的信息载体,分析了草图信息模型;基于手势操作,提出了协同上下文感知的概念和协同设计上下文描述模型;最后分析并给出面向同步编辑的草图交互设计和双向约束求解方法．所提出的协同设计方法自然简便,提高了设计效率,改善了人机交互方式．     

A global energy optimization framework for 2.1D sketch extraction from monocular images

The 2.1D sketch is a layered image representation, which assigns a partial depth ordering of over-segmented regions in a monocular image. This paper presents a global optimization framework for inferring the 2.1D sketch from a monocular image. Our method only uses over-segmented image regions (i.e., superpixels) as input, without any information of objects in the image, since (1) segmenting objects in images is a difficult problem on its own and (2) the objective of our proposed method is to be generic as an initial module useful for downstream high-level vision tasks. This paper formulates the inference of the 2.1D sketch using a global energy optimization framework. The proposed energy function consists of two components: (1) one is defined based on the local partial ordering relations (i.e., figure-ground) between two adjacent over-segmented regions, which captures the marginal information of the global partial depth ordering and (2) the other is defined based on the same depth layer relations among all the over-segmented regions, which groups regions of the same object to account for the over-segmentation issues. A hybrid evolution algorithm is utilized to minimize the global energy function efficiently. In experiments, we evaluated our method on a test data set containing 100 diverse real images from Berkeley segmentation data set (BSDS500) with the annotated ground truth. Experimental results show that our method can infer the 2.1D sketch with high accuracy.     

The background primal sketch: An approach for tracking moving objects

In this paper we present an algorithm that integrates spatial and temporal information for the tracking of moving nonrigid objects. In addition, we obtain outlines of the moving objects.Three basic ingredients are employed in the proposed algorithm, namely, the background primal sketch, the threshold, and outlier maps. The background primal sketch is an edge map of the background without moving objects. If the background primal sketch is known, then edges of moving objects can be determined by comparing the edge map of the input image with the background primal sketch. A moving edge point is modeled as an outlier, that is, a pixel with an edge value differing from the background edge value in the background primal sketch by an amount larger than the threshold in the threshold map at the same physical location. The map that contains all the outliers is called the outlier map. In this paper we present techniques based on robust statistics for determining the background primal sketch, the threshold, and outlier maps.In an ideal situation the outlier map would contain the complete outlines of the moving objects. In practice, the outliers do not form closed contours. The final step of the algorithm employs an edge-guided morphological approach to generate closed outlines of the moving objects. The proposed approach has been tested on sequences of moving human blood cells (neutrophil) as well as of human body motion with encouraging results.     

基于深度学习的草图分割算法综述

草图一直是人类传递信息的重要工具之一.草图可以通过简单明了的形式更快地表达人类的一些复杂思想,因此,草图处理算法一直是计算机视觉领域的研究热点之一.目前,对草图的研究主要集中在识别、检索和补全等方面.随着研究者对于草图细粒度操作的重视,对草图分割方面的研究也得到越来越多的关注.近年来,随着深度学习与计算机视觉技术的发展,出现了大量基于深度学习的草图分割方法,草图分割的精确度和效率也都得到了较大提升.但是,由于草图自身的抽象性、稀疏性和多样性,草图分割仍然是一个非常具有挑战性的课题.对基于深度学习的草图分割算法进行整理、分类、分析和总结,首先阐述了3种基本的草图表示方法与常用的草图分割数据集,再按草图分割算法的预测结果分别介绍了草图语义分割、草图感知聚类与草图解析算法,然后在主要的数据集上收集与整理草图分割算法的评测结果并对结果进行分析,最后总结了草图分割相关的应用并探讨未来可能的发展方向.     

On the ERA ranking representability of pairwise bipartite ranking functions

In domains like decision theory and social choice theory it is known for a long time that stochastic transitivity properties yield necessary and sufficient conditions for the ranking or utility representability of reciprocal preference relations. In this article we extend these results for reciprocal preference relations originating from the pairwise comparison of random vectors in a machine learning context. More specifically, the expected ranking accuracy (ERA) is such a reciprocal relation that occurs in multi-class classification problems, when ranking or utility functions are fitted to the data in a pairwise manner. We establish necessary and sufficient conditions for which these pairwise bipartite ranking functions can be simplified to a single ranking function such that the pairwise expected ranking accuracies of both models coincide. Similarly as for more common reciprocal preference relations, cycle transitivity plays a crucial role in this new setting. We first consider the finite sample case, for which expected ranking accuracy can be estimated by means of the area under the ROC curve (AUC), and subsequently, we further generalize these results to the underlying distributions. It turns out that the ranking representability of pairwisely compared random vectors can be expressed elegantly in a distribution-independent way by means of a specific type of cycle transitivity, defined by a conjunctor that is closely related to the algebraic product.     

一种用于快速草图设计的草图单元特征插入法

具有局部相似结构的复杂零件草图,其草图几何以及施加的约束重复操作,设计效率低下。文章提出了一种草图单元特征插入的新方法,把局部相似部分作为一个二维单元特征加入到当前设计的草图中,从而提高参数化设计程度和设计效率。分析了草图单元特征的特点,提出了关键技术的解决方法,最后给出了一个实例验证。     

三维手绘CAD系统的设计与表达

描述了一个基于手绘草图的三维设计系统,并给出了该系统的体系结构．该系统采用以草绘手势规则和草图语义自动机为基础的设计与表达的思路,描述了草图语义的获取、表达和理解方法,从而较好地支持了早期的三维产品概念设计．该系统以手写笔和手写板为交互输入设备,能够自然、高效地进行一些复杂的三维实体和三维场景设计．     

动画素描探究

无论冠以何种称谓,天底下只有一种素描,然而在艺术教育中,可以根据不同专业特点对素描教学进行一定的侧重,在此基础上动画素描这一概念是成立的。为了使素描更好地为动画艺术创作服务,我们既需要从传统素描中提取有益的因素,也需要对传统素描训练方法进行必要的改良。     

An explicit approach to minimal realization from system Markov parameters

A new method for determining a minimal realization of a finite-dimensional linear system from data comprising a set of Markov parameters is presented. The method is based on treating the Markov parameter matrices as the elements of vectors in an inner product space. The novel feature of this approach is the explicit determination of the minimal polynomial Known algorithms [3], [5] may then be used to get a minimal realization.     

结合改进Surf特征的素描人脸识别

素描人脸识别属于异质人脸识别范畴,是刑侦领域的研究热点。根据素描人脸识别的特点,对已配准的人脸图像进行伪素描转化,并用Surf算法提取伪素描图像对的特征点。对经过提取后的伪素描特征点进行坐标邻域一致性优化,排除坐标邻域相对位置不一致的特征点,最后统计伪素描图像对的有效特征点,以实现识别的目的。利用现有的素描人脸库,进行实验验证,在选取50个特征点时的识别率达到99%,验证了算法的有效性。该算法经优化后,可用于素描人脸识别。     

有限色彩空间下的线稿上色

目的 线稿上色是由线条构成的黑白线稿草图涂上颜色变为彩色图像的过程,在卡通动画制作和艺术绘画等领域中是非常关键的步骤。全自动线稿上色方法可以减轻绘制过程中烦琐耗时的手工上色的工作量,然而自动理解线稿中的稀疏线条并选取合适的颜色仍较为困难。方法 依据现实场景中特定绘画类型常有固定用色风格偏好这一先验,本文聚焦于有限色彩空间下的线稿自动上色,通过约束色彩空间,不仅可以降低语义理解的难度,还可以避免不合理的用色。具体地,本文提出一种两阶段线稿自动上色方法。在第1阶段,设计一个灰度图生成器,对输入的稀疏线稿补充线条和细节,以生成稠密像素的灰度图像。在第2阶段,首先设计色彩推理模块,从输入的颜色先验中推理得到适合该线稿的色彩子空间,再提出一种多尺度的渐进融合颜色信息的生成网络以逐步生成高质量的彩色图像。结果 实验在3个数据集上与4种线稿自动上色方法进行对比,在上色结果的客观质量对比中,所提方法取得了更高的峰值信噪比（peak signal to noise ratio,PSNR）和结构相似性（structural similarity index measure,SSIM）值以及更低的均方误差;在上色结果的色彩指标对比中,所提方法取得了最高的色彩丰富度分数;在主观评价和用户调查中,所提方法也取得了与人的主观审美感受更一致的结果。此外,消融实验结果也表明了本文所使用的模型结构及色彩空间限制有益于上色性能的提升。结论 实验结果表明,本文提出的有限色彩空间下的线稿自动上色方法可以有效地完成多类线稿的自动上色,并且可以简单地通过调整颜色先验以获得更多样的彩色图像。