非规则边界的图像镶嵌方法

图像镶嵌在图像处理及应用中具有重要的作用。在镶嵌图像时,通常采用的直线镶嵌法,往往难以选择一条理想的镶嵌边界线,以获得整个图像信息的良好效果。本文拟就非规则边界的图像镶嵌及处理方法作一介绍。图像镶嵌技术是计算机中常用的方法。每一幅陆     

建筑物矢量辅助的正射影像镶嵌线网络选择方法

为提高城市大比例尺正射影像制作效率,提出了一种建筑物矢量辅助的城市大比例尺正射影像镶嵌线网络自动选择方法。首先,利用建筑物房顶矢量联合数字高程模型自动生成建筑物简易模型,并得到建筑物在单片正射影像上的成像区域;然后,利用测区所有影像像底点位置自动生成测区初始Voronoi图镶嵌线网络并简化处理;最后,基于建筑物成像区域对网络中所有节点和镶嵌线进行自动优化选择,得到整个测区绕开建筑物成像区域的最优镶嵌线网络。实验结果显示,所提出方法在城市大比例尺正射影像镶嵌中不仅能够快速得到绕过建筑物的镶嵌线网络,并且保留了Voronoi图网络投影变形理论最小的特点,为城市大比例尺正射影像的镶嵌提供了一种新的方法。     

基于小波变换的图像镶嵌技术的研究

提出了一种基于小波变换的图像镶嵌的方法，小波变换具有多分辨分析特性，极适合解决图像镶嵌边缘灰度不连续问题。还提出了一种新的图像边界处理算法，对镶嵌图像边界作了精确处理，保证图像能够完全恢复，该边界处理算法适用于任何基于正交变换的小波数字滤波器，试验表明该方法具有良好的视觉效果。     

单机模式下的高分遥感影像并行镶嵌

针对传统串行镶嵌在单机模式下效率低下的问题,提出一种基于单机模式的小规模遥感影像并行镶嵌方法。通过对串行镶嵌过程的分析,将有效镶嵌区域按照处理内容划分为不同类型的数据子块,采用经典的"生产者-消费者"模型,实现了数据处理与磁盘I/O的解耦,以串行流水线的工作模式最大程度地隐藏了数据处理时间,从而有效提高了镶嵌效率。与商用软件ArcGIS进行了镶嵌效率对比,在小规模遥感影像整幅镶嵌应用中,该方法获得了2倍左右的加速效果。     

不同季相SPOT5影像镶嵌前色调处理方法研究

只有少数影像可供选择时,如何镶嵌季相差异大的影像,以取得较好的镶嵌效果,是一个很常见的技术问题。该问题的难点主要在于如何减小镶嵌影像间色调的差异。以厦门市两景不同年份、不同季相、色调差异很大的SPOT5卫星影像为例,采用数值调整,栅格编辑填充和特征信息提取、分类等图像处理方法,对影像上色调差异很大的斑块状地物和不规则零碎地物进行处理,达到了减小两景影像中同一地物特征色调差异的目的。文中提出的均色方法可以改善影像镶嵌效果,具有较强的实用性。     

TM图象数字镶嵌的几何精度分析及镶嵌方法的探讨

本文对ＴＭ镶嵌图象的内部精度进行分析后指出，传统的利用选取控制点建立图象间坐标转换方程，并利用此方程对图象进行处理、实验图象镶嵌的方法，在保证镶嵌图象几何精度方面存在头不足，用此方法得到的ＴＭ镶嵌图象的内部几何误差约８个象元；对传统的图象数字镶嵌方法进行分析的基础上，笔者总结大量工作的经验并参照前人的作法，在选定的地图投影下利用旋转方法对ＴＭ图象进行处理，进而完成镶嵌工作。     

基于特征不变描述的图像无缝镶嵌技术研究

在图像镶嵌算法中,SIFT算法本身就具有非常强的匹配能力,它可以处理两幅图像之间存在着的平移、旋转、尺度缩放等仿射变换,因此它是现今图像镶嵌中比较常用的方法。但在图像镶嵌中,如果直接使用SIFT算法会使运算量非常庞大,影响速度。针对这一问题,文中首先利用相位相关法来确定图像之间大致的重叠区域,再在大致的重叠区域提取SIFT特征点;其次利用特征点实现配准,并且在全局参数优化时考虑了径向畸变;最后用金字塔融合算法对图像进行融合。实验结果表明该算法能有效提高图像镶嵌的速度和精度,速度约提升三分之一,实现了一幅无缝的全景图像。     

全景图像镶嵌中累积误差的分析与减少方法研究

针对全景图像镶嵌中累积误差的问题,提出了一种基于多次柱面投影的变换基准图策略。首先,为了将累积误差有效地分散到各相邻图像之间,并减少柱面投影变换的计算量,算法利用相位相关和多分辨率分解法对柱面投影算法进行了改进;然后,利用改进变换基准图的分层匹配策略对图像序列进行镶嵌,避免了误差的单向累积;最后,运用拉普拉斯算子对镶嵌图像分级融合,消除了镶嵌缝隙。实验结果表明,该方法可以大大减弱镶嵌过程中累积误差的影响,提高图像的镶嵌精度。     

一种基于动态分组策略和多线程并行IO的并行镶嵌算法优化

遥感图像的镶嵌处理具有数据量大,流程复杂,算法处理耗时巨大的特点,并行计算是加速镶嵌处理过程速度的有效手段。但是,传统的并行镶嵌算法由于任务分配采用静态策略,导致计算节点负载不均衡,并行效率不高。同时,由于传统并行镶嵌算法中存在大量非常耗时的数据存取操作,并且在重采样和匀色过程中存在不合理的流程配置,使得并行效率降低,难以得到比较线性的加速比。本文提出的基于动态任务分配和多线程并行I/O的并行镶嵌算法,较好地解决了上述问题,通过对比分析和实验表明,本算法对大规模图像的镶嵌处理,具有较好的并行处理速度,以及理想的线性并行加速比曲线,节点扩展能力较强。     

一种基于特征的航空遥感影像自动镶嵌方法

提出了一种基于改进的Harris角点检测的航空遥感影像镶嵌方法。该方法增加了水平、垂直方向的梯度检验,用于提高整个算法的运算速度;增加了自适应阈值的确定算法,提高了整个算法的鲁棒性,实现了航空影像间的自动配准,最终使用加权平滑算法完成了图像的无缝镶嵌。整个处理过程完全自动地实现了对两幅航空遥感影像的无缝镶嵌,克服了传统航空遥感影像镶嵌在属性条件变化下的局限性,实验结果验证了方法的有效性。     

Intelligent hybrid system for dark spot detection using SAR data

Synthetic Aperture Radars (SAR) are the main instrument used to support oil detection systems. In the microwave spectrum, oil slicks are identified as dark spots, regions with low backscatter at sea surface. Automatic and semi-automatic systems were developed to minimize processing time, the occurrence of false alarms and the subjectivity of human interpretation. This study presents an intelligent hybrid system, which integrates automatic and semi-automatic procedures to detect dark spots, in six steps: (I) SAR pre-processing; (II) Image segmentation; (III) Feature extraction and selection; (IV) Automatic clustering analysis; (V) Decision rules and, if needed; (VI) Semi-automatic processing. The results proved that the feature selection is essential to improve the detection capability, keeping only five pattern features to automate the clustering procedure. The semi-automatic method gave back more accurate geometries. The automatic approach erred more including regions, increasing the dark spots area, while the semi-automatic method erred more excluding regions. For well-defined and contrasted dark spots, the performance of the automatic and the semi-automatic methods is equivalent. However, the fully automatic method did not provide acceptable geometries in all cases. For these cases, the intelligent hybrid system was validated, integrating the semi-automatic approach, using compact and simple decision rules to request human intervention when needed. This approach allows for the combining of benefits from each approach, ensuring the quality of the classification when fully automatic procedures are not satisfactory.     

Landsat-8长条带影像正射校正

目的 Landsat-8传感器采用线阵推扫式成像,通过分景处理获得标准景产品。面对大范围遥感数据需求,长条带数据具有更高的应用价值。长条带数据的一般获取方法是通过拼接标准景正射产品的方式,该方法处理效率不高,并且当条带中某景由于云覆盖量较多无法生产正射产品时,将无法通过多景拼接的方式生成相应的长条带正射产品。针对此方法存在的问题,本文提出一种Landsat-8长条带影像的正射校正方法。方法 以长条带影像为整体,通过控制点匹配、长条带几何精校正和正射校正3个部分,直接生成长条带级别的正射校正产品。在长条带几何精校正过程中,提出了Landsat-8的基于轨道约束的长条带平差模型及控制点优化选取方法。结果 在15景的条带长度范围内,本文方法生成的长条带正射产品的几何精度在12 m以内,满足Landsat-8正射产品的精度要求,且处理效率相较于标准景拼接方式提升1倍左右;对于云覆盖较多的景,利用连续3景进行长条带正射校正,可以得到与标准景正射产品几何精度相当的长条带正射产品。结论 本文提出的长条带处理方法,在一定长度范围内,能够得到满足Landsat-8正射产品的精度要求的长条带正射产品,处理效率得到较大提高,且能够有效克服传统方法中云覆盖情形对长条带产品获取的限制。     

基于灰关联分析的遥感影像无缝拼接*

根据中心像元与周围像元之间的邻近像元效应,提出了一种基于灰关联分析的多景遥感影像无缝拼接方法。该方法以影像重叠区域中心像元邻域作为参考序列与比较序列,利用斜率关联度计算两者之间的灰关联度,找到一条影像色调和纹理差异较小的拼接线,并对其两侧作加权灰度平滑处理,以消除拼接图像之间因色调差异造成的接缝效应。实验结果表明,该方法算法简单,易于实现,影像拼接质量较好。     

Aerial image mosaicking based on the 6-DoF imaging model

ABSTRACT

Image mosaicking technology is widely used in remote sensing and imaging of unmanned aerial vehicles (UAVs) for its superiority of generating large seamless images with high resolutions. Existing methods generally adopt the 8-DoF (degrees of freedom) homography camera model for image mosaicking, which require large computation cost in parameter optimization and cause distortions in the mosaicked images because of the accumulation errors. In view of this, this paper introduces an efficient mosaicking method based on 6-DoF imaging model to improve the quality of aerial image mosaicking. This derived model reduces the number of unknown variables for parameter optimization, hence improves the time efficiency. Meanwhile, a constraint term is merged into the objective function of optimization by analysing the characteristic of UAV imaging to eliminate the accumulation error in the mosaicking process. The experimental results on multiple datasets demonstrate that the proposed method achieves more accurate mosaicking results efficiently and is robust to different reference images relative to the state-of-the-art method.     

对西藏“一江两河”遥感影像镶嵌并进行拼接缝消除及分类

对现有的西藏中部10 景ETM+ 数据进行了假彩色合成, 并对合成影像进行了镶嵌。为便于分类, 对镶嵌影像进行了拼接缝消除的优化处理, 对消除了拼接缝的镶嵌影像进行了行政界叠加, 取行政界内影像进行分类, 将分类结果进行了统计和分析。     

Extracting road centrelines from high-resolution satellite images using active window line segment matching and improved SSDA

This paper presents a new semi-automatic approach to extracting main road centrelines from high-resolution satellite images. The approach is based on active window line segment matching and an improved sequential similarity detection algorithm (SSDA). First, a user-specified point on the road centreline is selected as a reference central point to define a template window, and a thresholding operation is performed within the window. Then a best matched target window along the road is searched to determine the next central point in the road. To avoid the influence of noise, only the line segment of ‘interest’ in the window is matched. An improved SSDA searching strategy is proposed to increase the matching speed. When the best matched target window is found, its centre is used as the next central point in the road, and a new template window is generated. By repeating the matching process, a series of central points can be obtained automatically and the corresponding final road centreline from them is extracted. Our approach also allows some kinds of user interventions in case automatic tracking fails. Experimental results confirm that the proposed approach is capable of rapidly and accurately extracting main road centrelines and has good robustness against noise.     

Unmanned Aerial Vehicle Localization Based on Monocular Vision and Online Mosaicking

This paper presents a new approach for vision-based UAV localization, using mosaics as environment representations. Inter-image motions are used to estimate the motion of the UAV. Online mosaicking is applied to reduce the impact of the accumulative errors in UAV position estimation. A new method to build an stochastic mosaic given the image-to-image homographies is detailed. The mosaic consists of a network of inter-image relations, and is used to create a consistent view of the environment of the UAV and hence, to detect the drift in position estimation by using the mosaic as a resource. The technique could be called simultaneous localization and mosaicking. This technique is specially suitable for monitoring and surveillance tasks in which the UAV will repeatedly cover the same area. The paper also shows experimental results with real UAVs where the benefits of the proposed method are evident.     

无人机载荷图像地理信息拼接及验证算法

In the traditional video and image processing technology field, researchers often focus on the processing of the image content, especially the accuracy and the speed. However, the geographic information data carried by UAV video and image is often ignored, resulting in the image only containing the scene information and losing the geographic data information after the image processing iscomplet- ed, so that the user cannot quickly obtain the geographic information of the target of interest from image processing results. In order to process the geographic information efficiently, an image mosaicking and verification algorithm for UAV image with geographic information regards geographic information data as multi-channel double floating-point matrix data, which can be calculated synchronously using matrix processing algorithms. Meanwhile, the accuracy and speed of a large number of image mosaicking tasks can be improved by using image-splicing algorithm based on grouping control with geographic information. The experimental results show that the proposed algorithm can effectively process the UAV image with geographic information, especially in image mosaicking.     

基于SVM的遥感图像半自动提取方法研究

遥感影像的半自动提取是遥感图像处理领域里的一个重要研究方向。提出一种新的半自动提取面状地物的方法,能够用随意给定的前景和背景曲线准确地提取出感兴趣的区域。算法首先提取前景和背景曲线上的像素作为分类样本,并使用SVM(Support Vector Machines)得到最初的分类效果。在此基础上,综合利用分类对象的光谱特征和形状特征信息,进行区域合并。最后,采用一种自动停止区域合并的准则确定最终合并结果。实验证明,该算法适用性强,可以在复杂多变的情况下,准确地区分出多种地物。     

面向区域布线的层次式PB角勾链版图数据结构

无网格区域布线具有存储量小、布通率较高、易实现混合设计规划布线并可解决串扰问题等优点,无网格区域布线算法中,找到路径后对底层图数据库的修改时间在整个算法运行时间中占很大比例,因此,操作简便、快捷的版图数据结构对于网格区域布线算法非常重要,目前无网格区域布线算法中应用最广泛的版图数据结构是矩形勾链,其点查找和模块插入操作的复杂度均匀Ｏ（Ｎ＾１／２）,文中提出一种新型的结合了Ｂｉｎ结构与梯形角勾链结构