块拼接纹理合成算法在图像拼接中的应用

小面积图像往往满足不了人们在工作中的需求，很多时候人们需要是大面积的图像，因此就需要一种算法来将相关的小范围拍摄的图像拼接成大图像，即实现全景图拼接。文中从块拼接纹理合成出发，并对块拼接纹理合成算法进行改进，将块拼接的原理应用到图像拼接上，并对像素加入与人视觉有关的权值进行接缝处理。实验结果表明，该方法简单实用，对于基本的由不同方位拍摄的图像都可以通过本算法进行拼接，并通过对接缝处的处理，取得了较好的结果。     

块拼接技术的改进及其在纹理传输中的应用

为了改善块拼接纹理合成图片在接缝处不平滑的现象,以及为了证明纹理传输约束的多样性,文中提出了一种改进的块拼接纹理合成技术,并把这种技术应用到了纹理传输中。文中对块拼接技术中最小切割路径的计算加入梯度结构信息,并且在选择匹配块时综合考虑重叠区域累计误差和最小切割路径,此外将改进的块拼接技术应用到纹理传输上,并对传输过程中依据的约束量的多样性进行探究。实验结果表明,改进的块拼接技术能够获得视觉上更好的合成结果,接缝处更加流畅连续,此外也验证了纹理传输中依据的两幅图像的对应约束量是多样的并不是单一的。     

一种基于自适应块拼接的纹理合成方法

纹理合成是当前计算机图形学、计算机视觉和图像处理领域的研究热点之一。本文在MRF模型和已有块拼接技术的基础上提出了一种自适应块拼接算法，该方法在全局最优的前提下进行不同大小纹理块的拼接，并使图像中的像素带有与视觉相关的权值，不仅在保证合成速度的同 时得到了更好的合成效果，而且从理论上统一了逐点合成和逐块合成两种基本方法。     

基于条块拼接的快速纹理合成

针对离线纹理合成算法所生成纹理占用较多存储空间的问题,提出一种所生成纹理可紧凑保存的快速纹理合成算法.该算法相继沿垂直和水平方向以条块拼接的方式合成纹理,合成结果可表示为一系列切割路径的组合,仅需保存这些切割路径即可在渲染时实时重建出纹理图像.通过在预处理中计算得到一组误差小的平行切割路径,合成时无需进行匹配,使得合成速度大幅提高.该算法对于在水平和垂直方向具有自相似性的纹理具有较高的合成质量.     

基于改进Harris-SURF的无人机图像快速拼接

无人机低空拍摄的图像具有成本低、方便快捷的优点,但也存在重叠度高、覆盖范围小等问题,需通过图像拼接来获得更大范围的图像。目前,无人机图像拼接效率不高。针对此问题,提出了一种结合Harris与SURF算法优点的改进Harris-SURF算法,并将该算法应用于无人机图像的自动配准;采用加权平滑融合算法消除亮度差异,较好地实现了无人机图像的无缝拼接。实验结果表明,该算法在效率方面较SURF算法有较大提高,对存在旋转、光照及视角变化的图像均有较好的匹配效果,实现了无人机图像的快速拼接。     

基于结构信息的图像拼接算法

研究了纹理较多、噪声较大的两幅或多幅的图像拼接问题.两幅图像拼接时,提取图像特征点的好坏对图像拼接结果有很大影响.经典的SIFT算法是一种较好的局部特征点提取算法.而对于纹理较多,噪声较大的图像中,SIFT算法会提取数量较大的特征点,影响匹配的准确性和速度.本文提出基于结构信息的图像拼接算法（SKM,Structual Keypoint Matching）,利用RTV算法提取图像的信息结构,有效地去除图像中的纹理噪声.去噪后,利用SIFT算法提取特征点进行匹配,最后利用RANSAC算法对匹配点对进行筛选,提高准确度.通过由SKM算法得到的变换矩阵H作用于原始图像,完成图像的拼接.     

基于投影模型和图像融合的拼接畸变消除算法

图像拼接技术是数字图像处理的一个重要分支,广泛运用于空间纹理检测、文物保护、医学图像、公安取证、虚拟现实等领域。由于拍摄的图像存在光照、角度、位移和抖动等各种因素影响,导致图像拼接时易造成图像畸变和变形。采取投影模型和图像融合,对畸变和变形进行研究,改进传统的拼接算法,提出一种自适应强、时效性高、稳定性好的投影模型和图像融合相结合的拼接算法。实验结果表明,该算法能够很好地消除拼接过程中产生的畸变和变形,并具有很好的鲁棒性。     

基于线匹配的图像拼接

提出一种图像拼接算法，通过确定两幅图像的最佳拼接线，不需要手工指定特征点，可对图像进行快速、自动无缝拼接。实验结果证明了该算法的有效性。     

一种柱面全景图像自动拼接算法

提出了一种基于特征块匹配的柱面全景图像拼接算法.首先将360度环绕拍摄的序列图像投影到柱面坐标系下;然后以一幅图像为基准图像,选择基准图像中边缘信息丰富的块作为基准块,利用特征块匹配法在待配准图像中找出与基准块匹配的配准块,进而实现两幅图像的配准;再根据配准结果计算出图像间的变换参数;最后采用平滑因子对两幅图像的重叠区域进行图像无缝拼接.实验证明,算法可以快速自动地生成柱面全景图像,具有良好的鲁棒性.     

大面积滚动指纹快速拼接算法

针对大面积滚动指纹采集和拼接在离线嵌入式系统中的应用,提出一种快速算法。对采集到的指纹图像进行增强处理,提取指纹块方向特征进行初次匹配,在此结果上利用纹理信息进行二次求精匹配,采用曲线缝合技术进行缝合。实验结果表明,该算法具有速度快、精度高、资源耗费小、鲁棒性好、适应性强、移植方便的特点,可满足实时嵌入式应用。     

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。     

Wide baseline image registration with application to 3-D face modeling

Establishing correspondence between features in two images of the same scene taken from different viewing angles is a challenging problem in image processing and computer vision. However, its solution is an important step in many applications like wide baseline stereo, three-dimensional (3-D) model alignment, creation of panoramic views, etc. In this paper, we propose a technique for registration of two images of a face obtained from different viewing angles. We show that prior information about the general characteristics of a face obtained from video sequences of different faces can be used to design a robust correspondence algorithm. The method works by matching two-dimensional (2-D) shapes of the different features of the face (e.g., eyes, nose etc.). A doubly stochastic matrix, representing the probability of match between the features, is derived using the Sinkhorn normalization procedure. The final correspondence is obtained by minimizing the probability of error of a match between the entire constellation of features in the two sets, thus taking into account the global spatial configuration of the features. The method is applied for creating holistic 3-D models of a face from partial representations. Although this paper focuses primarily on faces, the algorithm can also be used for other objects with small modifications.     

Fast panoramic stereo matching using cylindrical maximum surfaces.

This paper presents a fast panoramic stereo matching algorithm using a cylindrical maximum surface technique. The disparity for a pair of panoramic images is found in a cylindrical shaped correlation coefficient volume by obtaining the maximum surface rather than simply choosing a position that gives the maximum correlation coefficient value. The use of our cylindrical maximum surface technique ensures that the disparities obtained at the left and the right columns of the panoramic stereo images are properly constrained. Typical running time for a pair of 1324 x 120 images is about 0.33 s on a 1.7-GHz PC. A variety of real images have been tested, and good results have been obtained.     

Systems and Experiment Paper: Construction of Panoramic Image Mosaics with Global and Local Alignment

This paper presents a complete system for constructing panoramic image mosaics from sequences of images. Our mosaic representation associates a transformation matrix with each input image, rather than explicitly projecting all of the images onto a common surface (e.g., a cylinder). In particular, to construct a full view panorama, we introduce a rotational mosaic representation that associates a rotation matrix (and optionally a focal length) with each input image. A patch-based alignment algorithm is developed to quickly align two images given motion models. Techniques for estimating and refining camera focal lengths are also presented.In order to reduce accumulated registration errors, we apply global alignment (block adjustment) to the whole sequence of images, which results in an optimally registered image mosaic. To compensate for small amounts of motion parallax introduced by translations of the camera and other unmodeled distortions, we use a local alignment (deghosting) technique which warps each image based on the results of pairwise local image registrations. By combining both global and local alignment, we significantly improve the quality of our image mosaics, thereby enabling the creation of full view panoramic mosaics with hand-held cameras.We also present an inverse texture mapping algorithm for efficiently extracting environment maps from our panoramic image mosaics. By mapping the mosaic onto an arbitrary texture-mapped polyhedron surrounding the origin, we can explore the virtual environment using standard 3D graphics viewers and hardware without requiring special-purpose players.An erratum to this article can be found at     

视觉显著性驱动的全景渲染图非局部降噪

目的 传统降噪方法通常忽视人眼感知因素,对不同区域的图像块都进行同等处理。当使用传统降噪算法对全景画面滤波处理时,全景画面两极区域容易产生模糊问题,尤其是通过视口观察时,该问题更加明显。针对此问题,提出一种视觉显著性驱动的蒙特卡洛渲染生成全景图非局部均值（visual saliency driven non-local means,VSD-NLM）滤波降噪算法。方法 在VSD-NLM算法中首先使用全景图显著区域检测算法获取全景画面的显著区域;然后使用梯度幅值相似性偏差辅助的非局部均值（gradient magnitude similarity deviation assisted non-local means,GMSDA-NLM）滤波算法,降低显著区域的噪声;同时设计并行非局部均值（parallel non-local means,P-NLM）滤波算法,加快降噪处理速度,降低非显著区域噪声;最后利用改进的Canny算法提取梯度特征,同时结合各向异性扩散引导滤波来优化降噪结果。结果 采用结构相似度（structural similarity,SSIM）和FLIP作为评价指标,来对比VSDNLM算法与非局部均值滤波算法、多特征非局部均值滤波算法以及渐进式去噪算法等其他算法的性能。实验结果表明,VSD-NLM算法的降噪结果在客观评价指标上均优于对比算法,SSIM值比其他算法平均提高14.7%,FLIP值比其他算法平均降低15.2%。在视觉效果方面,VSD-NLM算法能够减轻全景画面模糊,提升视觉感知质量。本文对GMSDA-NLM和P-NLM算法的有效性进行了实验验证,相较于非局部均值滤波算法,GMSDA-NLM算法能够有效去除噪声并保持图像细节的完整性。P-NLM算法在运行速度方面相较对比算法平均提高约6倍,与串行算法生成的图像之间的SSIM值可达到0.996。结论 本文算法能够更好地用于全景图降噪,滤波效果更佳,对全景电影制作应用有重要的理论和实际意义。     

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。     

基于特征点匹配的全景图像拼接技术研究

提出了一种基于特征点匹配的全景图像拼接算法,首先提取各图像中的SIFT特征,通过特征点匹配完成两幅图像的配准;再根据图像配准结果计算出图像间的变换矩阵;最后采用渐入渐出加权平均的融合方法对两幅图像进行无缝拼接。实验表明,该算法具有匹配精度高、鲁棒性强等特点,可以快速而自动地生成全景图像。     

StitchingPHm—A new algorithm for panoramic images

In this paper it is presented a new algorithm for the construction of panoramic images (including 360 panoramas), which has as main characteristic to avoid the distortion that occurs by joining of several successive images in a sequence. We used the SIFT and RANSAC algorithms to find overlap areas between pairs of images, as well as a Blend algorithm for smoothing the joints. As the proposed algorithm doesn’t cause distortions, the subsequent correction is not necessary, contributing to a better performance. The results of experiments using commercial software and also the proposed algorithm were compared through a visual analysis. In addition, a quantitative analysis was done using numeric measures calculated on a panoramic image, generated from an image sequence of a region mapped and georeferenced by Google Earth.     

视频图像序列运动参数估计与动态拼接

本文采用多重分层叠代算法来估计全局运动参数，并提出应用于动态拼接的运动分割新方法，实现既有摄像机运动又有物体运动的视频图像序列自动拼接。我们的方法基本步骤如下：首先进行全局运动参数的初始估计，并且在分层叠代过程中进行区域分类，得到初始运动模板。接着空间分割原始图像，先根据图像的空间属性由底向上分层合并图像空间区域，再利用视频图像时间属性进一步向上合并，得到图像空间分割结果。然后结合初始运动模板和图像空间分割结果，采用区域分类新方法重新对图像空间分割结果的每个区域进行分类。然后根据分类结果逐步精确求解全局运动参数。最后进行图像合成，得到全景拼接图像。我们的方法利用了多重分层叠代的优点，并且充分考虑到视频图像空间和时间上的属性，实现了运动物体和覆盖背景的精确分割，避免了遮挡问题对全局运动参数估计精度的影响。而且在图像合成时我们解决了拼接图可能产生模糊或某些区域不连续等问题。实验结果表明我们的方法实现了动态视频图像序列高质量的全景拼接。     

A multicamera setup for generating stereo panoramic video

Traditional visual communication systems convey only two-dimensional (2-D) fixed field-of-view (FOV) video information. The viewer is presented with a series of flat, nonstereoscopic images, which fail to provide a realistic sense of depth. Furthermore, traditional video is restricted to only a small part of the scene, based on the director's discretion and the user is not allowed to "look around" in an environment. The objective of this work is to address both of these issues and develop new techniques for creating stereo panoramic video sequences. A stereo panoramic video sequence should be able to provide the viewer with stereo vision at any direction (complete 360-degree FOV) at video rates. In this paper, we propose a new technique for creating stereo panoramic video using a multicamera approach, thus creating a high-resolution output. We present a setup that is an extension of a previously known approach, developed for the generation of still stereo panoramas, and demonstrate that it is capable of creating high-resolution stereo panoramic video sequences. We further explore the limitations involved in a practical implementation of the setup, namely the limited number of cameras and the nonzero physical size of real cameras. The relevant tradeoffs are identified and studied.