面向影像地图色域映射算法研究

为了使影像地图跨媒介传递色彩失真最小,本文提出一种面向影像地图色域映射算法。首先,使用双边滤波对影像地图进行预处理,分解出低频和高频图像,根据人眼空间域视觉感知理论,对低频图像采用保护彩度裁切法,对高频图像采用保护明度压缩法,最后融合两幅映射后图像并再次映射至目标色域,使用图像结构相似度和S-CIELAB色差模型进行客观评价,并与HPMINΔE法、SGCK法及Bala提出算法进行比较。结果表明,面向影像地图色域映射算法在图像结构相似度和图像色差上都比其他算法稍好。因此,面向影像地图色域映射算法能提高影像地图的映射质量,可同时保护影像地图影像细节和矢量符号色彩。     

基于地图色域特征的色域映射算法研究

分析了地图色彩跨媒介传递出现偏色现象的原因。对地图色域特征进行了研究,提出了一种基于地图色域特征的地图种类划分方法,并指出针对每类地图设计相应色域映射算法的重要性。设计了一种面向线型设色地图的色域映射算法,该算法引入Sigmoidal型函数对地图进行明度压缩,对其色域点拟合出一条直线,把直线与明度轴交点作为映射中心点进行色域压缩。将该算法与ICC绝对色度意图映射法和SGCK算法进行对比,结果表明该方法较好于前两者并能够很好保持地图的整体色貌及颜色对比度,可以提高地图跨媒介色彩再现效果。     

基于色空间转换与色域映射的跨媒体颜色传输

通过分析跨媒体彩色图像传输过程中所面临的问题,引出了彩色图像传输中的关键技术——色空间转换与色域映射技术,并在分析色空间转换与色域映射的执行机制的前提下,介绍了色域边界的确定问题,同时对色域映射中的压缩和裁切的概念与应用进行了介绍,着重论述了当前领域内比较流行的算法,如SLIN、CUSP,并对它们进行了评价。     

基于色空间转换与色域映射的跨媒体颜色传输

通过分析跨媒体彩色图像传输过程中所面临的问题,引出了彩色图像传输中的关键技术——色空间转换与色域映射技术,并在分析色空间转换与色域映射的执行机制的前提下,介绍了色域边界的确定问题,同时对色域映射中的压缩和裁切的概念与应用进行了介绍,着重论述了当前领域内比较流行的算法,如SLIN、CUSP,并对它们进行了评价。     

跨媒介的地图色域映射方法研究

颜色设备相关性的特点导致地图在跨媒介再现时容易出现丢色、偏色等现象,影响地图视觉效果,甚至传输错误的属性、数量等信息。从地图色域特征出发,将地图色域映射问题转换为目标设备色域约束下的地图色域离散点云形变问题。进一步引入Delaunay剖分和几何矩,定义CIE1976LAB色空间下地图色域形变的目标函数,给出全局最优解的求解流程。将算法结果与ICC再现意图结果进行对比,结果表明该方法能够很好保持地图整体的色貌特征以及局部图斑之间的色彩对比、连续等色彩特征,能够显著提高地图跨媒介地图颜色复制精度。     

用标记法压缩色域

提出了一种新的色域压缩方法。用此种方法不仅能将超色域颜色压缩到目标设备的色域内,使色域内大部分颜色保护不变,而且能保证被压缩图像部分的灰色级不受损失;提出了判断色域的检测方法。试验证明,使用该检测方法处理的图像的超色域与用Photoshop中的色域警告处理的超色域非常相似。     

基于混合混沌序列的对称图像加密算法设计

通过时部分数字化混沌图像加密算法的分析研究,设计了一种混沌对称图像加密算法.该对称图像加密算法以Logistic映射和Chebyshev映射生成的混沌序列为初始序列,以AES算法的S盒变换和记忆存储作为非线性变换.实验结果证明,算法克服了初始混沌序列和初始信号的相关性,输出的序列满足平衡性、大周期、高线性复杂度和理想的相关特性等基本的密码特性.算法设计环节中加入了记忆成份和压缩环节,使得针对这两个混沌映射的现有分析方法不再有效,并且可以实现较高的加密速度.     

基于流形对齐的高光谱遥感图像降维和分类算法

多时相的高光谱遥感图像数据处理中会出现地物光谱特征漂移的现象。为了提高源域数据已有知识对目标域数据分类的精度,采用了基于流形对齐的分类算法。先用一个标准的线性或非线性的降维方法将2个高光谱遥感数据集映射到低维(流形)空间中,再用Procrustes分析方法将其低维嵌入之间的平移、旋转和缩放因子剔除,得到数据集间的最优对齐,最后用最近邻算法进行分类。对多个不同时相高光谱遥感图像进行实验,并对比了已有的流形对齐算法,结果表明本算法具体较好的迁移能力和分类效果。     

结合多混沌映射和输出反馈的图像加密算法

提出了一种结合多个Logistic混沌映射和逐段正弦混沌映射的图像加密算法。通过m个Logistic混沌映射的多次迭代,分别产生m个分段正弦混沌映射的初值和参数值,由m个分段正弦混沌映射迭代产生图像加密密钥序列,并引入密文输出反馈机制,对图像像素值逐点进行2轮异或加密。实验表明,该算法使密文对明文和密钥都充分敏感,加密图像像素值具有类随机均匀分布特性,相邻像素具有零相关特性,而且算法具有密钥空间大、加密速度快的优越性。     

矢量地图数据数字水印技术综述

矢量地图数据在网络环境下的共享机制,给各个领域都带来了极大的便利,但是其安全和版权保护问题也日益突出。数字水印技术作为版权保护的一种有效方法,成为人们关注的一个焦点。本文分析了矢量地图数据自身特点和常见处理方式;从建立映射关系、构造嵌入域、嵌入方式等3个步骤对空间域水印算法进行了详细分析,分析每种算法的优缺点,为下一步水印算法提供指导;对频率域水印算法进行了研究,并指出了频率域水印算法存在的问题;指出了矢量地图数据水印进一步的研究方向。     

Map Libraries

Colour distortion, which is caused by the unavoidable mismatch between a map’s gamut and a device’s gamut, negatively affects the semiotic quality of maps. Cartographic communication often suffers from undesirable colour inconsistency. This method models cartographic colour reproduction as a constrained transform problem, namely, adapting a map’s gamut to fit a device’s gamut while preserving the semiotic quality. First, the characteristics of the map’s gamut are investigated by considering cartographic principles, and the fundamental concerns of preserving semiotic quality are proposed. Then, the self-organizing map method is introduced to iteratively optimize the cartographic colour reproduction. We implement this method and evaluate it based on a series of thematic maps. The results indicate that the proposed algorithm offers better results than two alternatives in terms of facilitating cartographic colour reproduction.     

An Artificial Bee Colony-based Algorithm to Automatically Create Colour Schemes for Geovisualizations

Creating appropriate colour schemes is challenging for both novice and experienced cartographers. This paper introduces an artificial bee colony (ABC) algorithm to automatically create various colour schemes. Colour scheme creation is treated as a constrained search problem in a continuous colour space. We considered the gamut of the target device and a series of cartographic rules, such as convention, discrimination, contrast, perceptual uniformity and brightness mirror, in the ABC algorithm and presented detailed initialization, fitness definition, local exploration, and global exploration methods for creating qualitative, sequential and diverging colour schemes. The proposed method is evaluated with a case study, and the results indicate that compared with the brute force search method, the proposed method can create satisfying colour schemes of similar quality but significantly improved efficiency.     

数字原稿色域的定量分析与比较

提出了一种科学、准确地定量分析数字原稿色域的方法，通过相关实验比较了各种成像环境对数字原稿色域的影响，并获得了一些有价值的成果。     

贝塞尔大地反解问题的高效率算法

针对目前的贝塞尔大地反解算法中存在的问题，设计一种高效率的贝塞尔大地问题反解算法，解决了原算法存在的奇异问题，不需做繁锁的象限判定，计算方便易于编程实现。同时指出贝塞尔投影不同胚映射，不适用于距离太远的大地问题反解。     

基于空间自相关BP神经网络的遥感影像亚像元定位

亚像元定位技术是一种获取地物在混合像元中分布信息的有效方法.提出一种基于空间自相关函数的遥感影像BP神经网络亚像元定位方法,与传统的BP神经网路亚像元定位方法相比,该方法利用空间自相关函数Moran's I 在亚像素级上对定位结果进行约束,其结果更符合空间相关性假设理论.试验结果表明,该方法优于传统BP神经网络亚像元定...     

Cartographic News

This paper reports the results of an in-depth study which investigated two algorithms for line simplification and caricatural generalization (namely, those developed by Douglas and Peucker, and Visvalingam, respectively) in the context of a wider program of research on scale-free mapping. The use of large-scale data for man-designed objects, such as roads, has led to a better understanding of the properties of these algorithms and of their value within the spectrum of scale-free mapping. The Douglas-Peucker algorithm is better at minimal simplification. The large-scale data for roads makes it apparent that Visvalingam's technique is not only capable of removing entire scale-related features, but that it does so in a manner which preserves the shape of retained features. This technique offers some prospects for the construction of scale-free databases since it offers some scope for achieving balanced generalizations of an entire map, consisting of several complex lines. The results also suggest that it may be easier to formulate concepts and strategies for automatic segmentation of in-line features using large-scale road data and Visvalingam's algorithm. In addition, the abstraction of center lines may be facilitated by the inclusion of additional filtering rules with Visvalingam's algorithm.     

Applicability of Landsat 8 data for characterizing glacier facies and supraglacial debris

The present work evaluates the applicability of operational land imager (OLI) and thermal infrared sensor (TIRS) on-board Landsat 8 satellite. We demonstrate an algorithm for automated mapping of glacier facies and supraglacial debris using data collected in blue, near infrared (NIR), short wave infrared (SWIR) and thermal infrared (TIR) bands. The reflectance properties in visible and NIR regions of OLI for various glacier facies are in contrast with those in SWIR region. Based on the premise that different surface types (snow, ice and debris) of a glacier should show distinct thermal regimes, the ‘at-satellite brightness temperature’ obtained using TIRS was used as a base layer for developing the algorithm. This base layer was enhanced and modified using contrasting reflectance properties of OLI bands. In addition to facies and debris cover characterization, another interesting outcome of this algorithm was extraction of crevasses on the glacier surface which were distinctly visible in output and classified images. The validity of this algorithm was checked using field data along a transect of the glacier acquired during the satellite pass over the study area. With slight scene-dependent threshold adjustments, this work can be replicated for mapping glacier facies and supraglacial debris in any alpine valley glacier.