Adaptive Compositing and Navigation of Variable Resolution Images

We present a new, high‐quality compositing pipeline and navigation approach for variable resolution imagery. The motivation of this work is to explore the use of variable resolution images as a quick and accessible alternative to traditional gigapixel mosaics. Instead of the common tedious acquisition of many images using specialized hardware, variable resolution images can achieve similarly deep zooms as large mosaics, but with only a handful of images. For this approach to be a viable alternative, the state‐of‐the‐art in variable resolution compositing needs to be improved to match the high‐quality approaches commonly used in mosaic compositing. To this end, we provide a novel, variable resolution mosaic seam calculation and gradient domain color correction. This approach includes a new priority order graph cuts computation along with a practical data structure to keep memory overhead low. In addition, navigating variable resolution images is challenging, especially at the zoom factors targeted in this work. To address this challenge, we introduce a new image interaction for variable resolution imagery: a pan that automatically, and smoothly, hugs available resolution. Finally, we provide several real‐world examples of our approach producing high‐quality variable resolution mosaics with deep zooms typically associated with gigapixel photography.     

基于光照方向的人像合成图像的检测

数字篡改图像即使做的很逼真,没有留下肉眼可见的篡改证据,但图像原先的统计学规律已经改变.合成图像一般是将不同图像中的人或物体拼接到一起.由于光线是有方向的,所以在进行这种操作的时候图像的光线很难完全吻合,因此光线的不吻合可以作为判断篡改图像的依据.而单个图像的光照方向可以用Pentland方法估计出来,把篡改图像分割就可以得到图像不同部分的光照方向,并据此判断图像光照方向是否吻合.实验证明Pentland方法检测人像合成图像具有良好的效果.     

Constructing Virtual Cities by Using Panoramic Images

Simultaneously acquired omni-directional images contain rays of 360 degree viewing directions. To take advantage of this unique characteristic, we have been developing several methods for constructing virtual cities. In this paper, we first describe a system to generate the appearance of a virtual city; the system, which is based on image-based rendering (IBR) techniques, utilizes the characteristics of omni-directional images to reduce the number of samplings required to construct such IBR images. We then describe a method to add geometric information to the IBR images; this method is based on the analysis of a sequence of omni-directional images. Then, we describe a method to seamlessly superimpose a new building model onto a previously created virtual city image; the method enables us to estimate illumination distributions by using an omni-directional camera. Finally, to demonstrate the methods' effectiveness, we describe how we implemented and applied them to urban scenes.     

柱面全景图像拼合算法研究

IBR技术是近几年来在基于传统几何图形建模方法基础上发展起来的一种新的绘制方法,它用数码相机拍摄到的或计算机生成的照片来绘制新视点处的图像,具有绘制速度与场景的复杂度无关的特点。论文从实际应用的角度,提出并实现了图像拼合的新算法,新算法结合了手动拼合与自动拼合算法的优点,既可用于全景空间图像拼合,亦可用于普通图像的拼合,效率高。     

Processing Sparse Panoramic Images via Space Variant Operators

The use of omni-directional cameras has become increasingly popular in vision systems for video surveillance and autonomous robot navigation. However, to date most of the research relating to omni-directional cameras has focussed on the design of the camera or the way in which to project the omni-directional image to a panoramic view rather than the processing of such images after capture. Typically images obtained from omni-directional cameras are transformed to sparse panoramic images that are interpolated to obtain a complete panoramic view prior to low level image processing. This interpolation presents a significant computational overhead with respect to real-time vision. We present an efficient design procedure for space variant feature extraction operators that can be applied to a sparse panoramic image and directly processes this sparse image. This paper highlights the reduction of the computational overheads of directly processing images arising from omni-directional cameras through efficient coding and storage, whilst retaining accuracy sufficient for application to real-time robot vision.

基于全景图像的拼接算法研究

IBR技术不仅可以弥补传统基于几何绘制技术的不足,而且能给出更丰富的图像显示.论文从工程实际应用的角度出发,提出并实现了一种图像拼接的新方法.该方法即可用于全景控件图像的拼接,也可用于普通图像的拼接.试验证明,此方法在全景图像的生成中具有自动拼接、效率高等优点.     

一种基于自然图像统计模型的图像合成检测方法

Nowadays, digital images can be easily tampered due to the availability of powerful image processing software. As digital cameras continue to replace their analog counterparts, the importance of authenticating digital images, identifying their sources, and detecting forgeries is increasing. Blind image forensics is used to analyze an image in the complete absence of any digital watermark or signature. Image compositing is the most common form of digital tampering. Assuming that image compositing operations affect the inherent statistics of the image, we propose an image compositing detection method on based on a statistical model for natural image in the wavelet transform domain. The generalized Gaussian model (GGD) is employed to describe the marginal distribution of wavelet coefficients of images, and the parameters of GGD are obtained using maximum-likelihood estimator. The statistical features include GGD parameters, prediction error, mean, variance, skewness, and kurtosis at each wavelet detail subband. Then, these feature vectors are used to discriminate between natural images and composite images using support vector machine (SVM). To evaluate the performance of our proposed method, we carried out tests on the Columbia Uncompressed Image Splicing Detection Dataset and another advanced dataset, and achieved a detection accuracy of 92% and 79%, respectively. The detection performance of our method is better than that of the method using camera response function on the same dataset.     

全方位图像展开成全景和透视图的实现方法

全方位视觉系统生成的全方位图像能获得水平方向3600环境信息,非常适合于某些有大视场需求的应用。该文介绍了全方位图像的特点、生成原理及其展开成全景图及透视图的具体实现方法。同时也介绍了以DirectShow为工具,全方位视频的展开实现方法。最后通过实验证明了全景图及透视图生成方法的有效性。     

基于全景图像的虚拟漫游系统研究

提出一种基于全景图像的虚拟漫游方案。为了对不同视角的图像进行自动拼接,首先在图像的尺度空间中提取特征点,并赋予主方向。根据邻域信息计算得到特征向量后,利用最近邻特征点距离与次近邻特征点距离之比得到初始匹配点对。然后使用RANSAC(Random Sample Consensus)算法剔除错误匹配点对,同时计算得到图像之间的变换参数。完成图像拼接后,通过重投影算法可以生成场景在不同视线方向上的透视视图,让用户获得身临其境的沉浸感。     

一种精确匹配的全景图自动拼接算法

本文提出一种全景图像自动拼接算法,能够实现特征点对的精确筛选和匹配,以及输入图像的自动排序和拼接。首先提取输入图像的尺度不变特征变换SIFT特征点,并采用k-d树搜索得到图像之间所有初始特征匹配对;利用欧氏距离比值和中值滤波器对初始特征点对进行筛选后,再应用随机抽样一致算法RANSAC得到图像间精确匹配的特征点对;计算出图像之间的单应性矩阵,在此基础上完成对输入图像的自动排序和配准,最终拼接合成全景图像。实验结果表明,该算法能获得比结合欧氏距离比值的RANSAC算法更高的配准精度,全景图拼接效果较好,具有良好的鲁棒性。     

基于球面全景图的空战环境漫游研究

研究鱼眼图像的拼接算法,实现利用两幅鱼眼图像生成球面虚拟空间,然后探讨基于球面虚拟图的多视点漫游问题,利用反投影模板技术有效地提高全景图浏览的速度,采用缩放的方法改进了行进间的浏览效果,从而提高虚拟漫游的沉浸感,具有一定的实用意义。     

基于特征线段的图像快速拼接算法

在讨论图像拼接的模板匹配法的基础上,针对计算量太大的问题,提出了一种提高效率的改进算法。选取四条特征线段做为模板,并利用相邻图像之间的颜色信息进行图像拼接。试验结果表明,改进算法不但降低了计算复杂度,还很好的保证了拼接质量。     

一种360度柱面全景图快速生成算法

全景图像是构造虚拟环境的基本要素之一,本文提出了一种新的360柱面全景图绘制算法。首先对原始图像进行柱面投影,然后通过对图象重叠部分的对应特征区域进行匹配和拼合来实现图象无缝镶嵌。实验表明该算法运算量较小,能有效、快速地生成柱面全景图。     

基于环视图象的数字相机内参数自定标方法

描述了一种适用于IBR系统的数字相机内参数自定标方法。该方法基于跟踪机机旋转得到的图象系列的特征匹配点以,而不需要标定物。认定在相机旋转过程中,其光学中心是稳定不变的,也即图象中心是固定的,可以事先定标;但容许相机的焦距在各幅图象间有变化,利用真实图象序列进行了实验验证,表明该方法能鲁棒地估算相机内参数。     

一种基于凸曲面反射镜的柱面全景图像无缝快速生成系统

全景图像在虚拟场景绘制和监控等领域有着广泛的应用。传统的全景图像生成需要在一个视点拍摄多张、多角度有边界重叠的图像再进行拼接,拍摄要求很高,制作繁琐。本文设计了一种新的全景图像生成系统,在一个视点只需拍摄一张图像,经过变换即可得到360度柱面全景图像。     

基于全景图像CNN的隧道病害自动识别方法

针对目前隧道衬砌病害检测过程中难以快速、方便地获取隧道内壁全景图像以及难以自动检测识别各种病害等问题,提出一种基于全景图像CNN的隧道病害自动识别方法。首先通过一种全景视觉传感器快速获取隧道内壁的全景图像;然后对全景图像进行处理,主要通过全景图像展开、图像预处理、二值化处理等操作来提取疑似病害区域;最后,采用卷积神经网络对病害进行自动检测分类识别。实验结果表明,所提方法极大程度地简化了检测装置在获取隧道内壁全景图像的结构,通过端对端的卷积神经网络实现了各种隧道病害特征的自动提取、检测和识别,并具有88%的检测识别精度,为隧道的维护、竣工验收提供了有效的技术支撑。     

Tour Into the Picture using a Vanishing Line and its Extension to Panoramic Images

Tour into the picture (TIP) proposed by Horry et al. ¹³ is a method for generating a sequence of walk-through images from a single reference picture (or image). By navigating a 3D scene model constructed from the picture, TIP produces convincing 3D effects. Assuming that the picture has one vanishing point, they proposed the scene modeling scheme called spidery mesh. However, this scheme has to go through major modification when the picture contains multiple vanishing points or does not have any well-defined vanishing point. Moreover, the spidery mesh is hard to generalize for other types of images such as panoramic images. In this paper, we propose a new scheme for TIP which is based on a single vanishing line instead of a vanishing point. Based on projective geometry, our scheme is simple and yet general enough to address the problems faced with the previous method. We also show that our scheme can be naturally extended to a panoramic image.     

Accurate Junction Detection and Characterization in Natural Images

Accurate junction detection and characterization are of primary importance for several aspects of scene analysis, including depth recovery and motion analysis. In this work, we introduce a generic junction analysis scheme. The first asset of the proposed procedure is an automatic criterion for the detection of junctions, permitting to deal with textured parts in which no detection is expected. Second, the method yields a characterization of L-, Y- and X- junctions, including a precise computation of their type, localization and scale. Contrary to classical approaches, scale characterization does not rely on the linear scale-space. First, an a contrario approach is used to compute the meaningfulness of a junction. This approach relies on a statistical modeling of suitably normalized gray level gradients. Then, exclusion principles between junctions permit their precise characterization. We give implementation details for this procedure and evaluate its efficiency through various experiments.     

Adobe Premiere CS4中数字视频合成技术的实现

视频合成就是要将多个视频画面融合为一个视频画面,它是数字视频编辑中的一个重要问题。在Adobe Premiere CS4视频编辑软件中,提供了多种技术手段来解决这一问题。本文介绍通过调整素材的透明度和设置视频剪辑的＂混合模式＂来完成视频合成;通过视频特效组中的滤镜,根据素材的颜色、亮度、无用信号以及遮罩进行抠像,以达到视频合成的目的;使用＂轨道遮罩键＂特效实现跟踪画面的视频合成技术。实践证明,灵活地使用这些方法可以制作出高效、自然的数字视频作品。