Boundaries detection and color correction of shadows in color images

The paper under consideration deals with information technology for correction of shadow artifacts on color digital images obtained by taking photos of paintings with the purpose of their reproduction. Appearance of shadow artifacts is caused by different intensity of picture lighting. The problem of shadow detection and subsequent color correction in this area is solved.     

Linear array for spelling correction

This paper introduces a linear array for spelling correction using 15 processors. Many architectures have been proposed to solve similar string correction problems such as speech recognition or nucleic acid sequence computation. It is known that the hypercube, de Bruijn and grid networks contain a Hamiltonian path, a path which contains all the vertices of the network. The execution time of spelling correction on all of these networks is equal. © 1997 John Wiley & Sons, Ltd.     

Pixel distribution shifting color correction for digital color images

This paper is concerned with a proposed color correction method called the Pixel Distribution Shifting Color Correction (PDSCC). This method employs a shifting process on the pixel distribution of a color image to correct its white reference point and ensure the white reference point is achromatic. The proposed method has been tested on numerous types of images which include indoor, outdoor, and underwater images. The qualitative and quantitative analyses have shown ample evidence that the proposed method outperforms some state-of-the-art methods, such as the Grey World, the White Patch and the General Grey World methods. The resultant images are viewed to be more natural and suggest more pleasant visualization without the intervention of the saturation problem.     

Spectral characterization and color correction of display colorimeters

Abstract— Tristimulus colorimeters commit systematic errors due to their imperfect realization of the CIE color‐matching functions. A method is proposed to characterize display colorimeters in a single session using a monochromator independently of any display. Colorimeter spectral responsivity functions are obtained that then serve to predict correction matrices for all the possible displays. Experiments show that this can be done with sufficient accuracy to meet practical requirements.     

Accurately estimating reflectance parameters for color and gloss reproduction

A new method is described to estimate diffuse and specular reflectance parameters using spectral images, which overcomes the dynamic range limitation of imaging devices. After eliminating the influences of illumination and camera on spectral images, reflection values are initially assumed as diffuse-only reflection components, and subjected to the least squares method to estimate diffuse reflectance parameters at each wavelength on each single surface particle. Based on the dichromatic reflection model, specular reflection components are obtained, and then subjected to the least squares method to estimate specular reflectance parameters for gloss intensity and surface roughness. Experiments were carried out using both simulation data and measured spectral images. Our results demonstrate that this method is capable of estimating diffuse and specular reflectance parameters precisely for color and gloss reproduction, without requiring preprocesses such as image segmentation and synthesis of high dynamic range images.     

Fast color correction using principal regions mapping in different color spaces

A color correction method for balancing the color appearances, among a group of images, about a specified object or scene, such as panoramic images and object movies, is developed and tested in this paper. In order to increase the running speed of color correction and reduce the out-of-gamut color pixels, we introduce the selection of principal regions. The average color values of principal regions are used to construct the low-degree (up to degree two) polynomial mapping functions from the source images to the corrected images. The functions are run in the decorrelated color spaces. Our method is tested using real and synthetic images. The results of these tests show the proposed method can get a better performance than other existing methods.     

彩色图像的单应矩阵估计算法

图像间单应矩阵估计是图像配准与图像拼接中的核心问题,传统的估计方法是针对灰度图像的算法。本文以分层运动估计为基础提出了彩色图像的平面单应矩阵的估计算法。此算法采用色度与饱和度不变为约束条件得到彩色图像的光流方程,显著改善了亮度不变约束的不足之处;采用最优导数计算滤波器计算图像导数,提高了算法的精度与稳健性;采用尺度总体最小二乘方法代替最小二乘或总体最小二乘方法来估计模型参数,提高了算法对于图像噪声的适应性。实验结果表明,该算法稳健性好、精度高,而且可以得到稠密的匹配点。     

Automatic color correction for multi-projector display systems

A hierarchical color correction framework is presented to automatically calibrate multiple projectors. The proposed framework consists of two sub-methods: a simple color correction method and an advanced color correction method. An automatic selection scheme is designed to choose between the two sub-methods according to specific conditions. The simple color correction method uses a parameter model to map projected images into the Common Achievable Response (CAR) space for color consistent outputs. The advanced color correction method takes the projector properties, the display surface optical properties, and the relative distances between the screen and the projectors into consideration. A pre-processing step is designed to eliminate isolated abnormal sampling points, resulting in better quality outputs. In the experiment part, the effectiveness of the proposed framework is verified with both front projection systems and rear projection systems. The experimental results show that the proposed framework achieves better calibration results comparing with traditional methods.     

多视点视频编码去相关颜色校正

多视点视频编码效率受到各个视点图像之间颜色不均衡的影响。在三色激励值近似线性无关的lαβ颜色空间中,对多视点视频数据实现了颜色校正。根据视频序列原始数据的特点,选择合适的变换矩阵,提供了YUV到lαβ空间的变换式。为降低不同视点间亮度差异的影响,在块搜索和匹配中结合相关分析法,获取最优匹配块。将匹配块数据变换到从lαβ衍生的一个线性无关的颜色空间中,采用统计量逼近的方法对数据进行了更简便的校正。结果表明,所校正的数据变换回YUV空间后,主观效果良好,消除了颜色差异,在编码性能上,Y分量平均PSNR提高达l.4dB以上,证明了该颜色校正算法的有效性。     

改进的基于颜色滤波阵列特性的篡改检测

随着图像编辑软件的普及,数字图像可以很容易地被编辑和修改,但如果恶意篡改,后果可能会非常严重,因此图像篡改检测越来越重要。大部分数码相机都使用单传感器和颜色滤波阵列,并通过插值获得彩色图像。插值引入了相关性,而篡改操作会破坏这种相关性,可以使用EM算法对其进行检测。通过对已有模型进行改进,用拉普拉斯分布代替插值点残留误差的正态分布,使分布情况更符合实际。实验证明该算法可以检测出不同插值算法下的篡改痕迹,并且改进后的模型加快了EM算法的收敛速度,缩短了篡改检测的时间。     

Robust estimating equations and bias correction of correlation parameters for longitudinal data

The estimation of correlation parameters has received attention for both its own interest and improvement of the estimation efficiency of mean parameters by the generalized estimating equations (GEE) approach. Many of the well-established methods for the estimation of correlation parameters can be constructed under the GEE framework which is, however, sensitive to outliers. In this paper, we consider two ways of constructing robust estimating equations for achieving robust estimation of the correlation parameters. Furthermore, the estimators of the correlation parameters from the robustified GEE may be still biased as the expectation of the estimating equation is biased from zero when the underlying distribution is not symmetric. Therefore, bias-corrected robust estimators of correlation parameters are proposed. The performance of the proposed methods are investigated by simulation. The results show that the proposed robust and bias-corrected robust estimators can reduce the bias successfully. Two real data sets are analyzed for illustration.     

利用颜色滤波阵列特性和模糊估计检测篡改

由于有功能强大的计算机和图像处理软件的存在,普通用户可以将数字图像篡改成他们想得到的任何形式.如果这些篡改图用在媒体或法律上,对社会将造成很大的影响,所以检测数字篡改变成了一个非常严峻的问题.在大多数情况下,数字篡改图像是很逼真的,但是在处理过程中也会留下一些痕迹.将图像的颜色滤波阵列特性和模糊估计的方法结合起来对图像进行篡改检测,对多幅图像操作,实验证明有不错的检测效果.     

Application of underwater hyperspectral data for color correction purposes

Color correction of underwater images has been considered a difficult task for a number of reasons. Those include severe absorption of the water column, the unpredictable behavior of light under the water surface, limited access to reliable data for correction purposes, and the fact that we are only able to process three spectral channels, which is insufficient for most color correction applications. Here, the authors present a method to estimate a hyperspectral image from an RGB image and pointwise hyperspectral data. This is then used to color correct the hyperspectral underwater image and transform it back into RGB color space.     

Simultaneous image color correction and enhancement using particle swarm optimization

Color images captured under various environments are often not ready to deliver the desired quality due to adverse effects caused by uncontrollable illumination settings. In particular, when the illuminate color is not known a priori, the colors of the objects may not be faithfully reproduced and thus impose difficulties in subsequent image processing operations. Color correction thus becomes a very important pre-processing procedure where the goal is to produce an image as if it is captured under uniform chromatic illumination. On the other hand, conventional color correction algorithms using linear gain adjustments focus only on color manipulations and may not convey the maximum information contained in the image. This challenge can be posed as a multi-objective optimization problem that simultaneously corrects the undesirable effect of illumination color cast while recovering the information conveyed from the scene. A variation of the particle swarm optimization algorithm is further developed in the multi-objective optimization perspective that results in a solution achieving a desirable color balance and an adequate delivery of information. Experiments are conducted using a collection of color images of natural objects that were captured under different lighting conditions. Results have shown that the proposed method is capable of delivering images with higher quality.     

基于长线列探测器的图像非均匀性研究与校正

基于长线列图像探测器的成像系统,其图像的非均匀性往往制约着系统成像的质量.结合线列图像探测器的结构特点,分析了线列图像的非均匀性产生原因,并在此基础上分析了多点校正算法,并提出一种基于图像轮廓提取的图像平滑算法.通过对比处理前后的结果,采用图像轮廓提取的图像平滑算法,在保证图像细节的基础上,能够提高图像的均匀性.     

基于标准白色模板的扩展RGB颜色校正算法

如何通过颜色校正获得真实的颜色重现已成为图像处理中普遍存在的技术难点。针对此类问题,提出一种基于白色模板的颜色校正方法：首先将颜色空间的精度扩展到一定的程度,然后制作一个标准状态下的白色模板;接着根据条件选取适当的校正算子,根据校正算子得出的RGB值去校正在同样条件下得到的目标图像。工程实践和仿真结果表明,校正后的图像不但在视觉上与标准图像达到一致,并且在数值误差上也小于传统的校正方法。     

基于同态滤波的水下图像增强与色彩校正模型

水体对于不同波长的光信号衰减程度不一致,这种现象破坏了水下图像的清晰度和色彩恒定性。为了解决水下图像亮度与色彩扭曲问题,提出一种基于同态滤波的水下图像增强与色彩校正模型。首先,通过比尔-朗伯定律和路径辐射分量构建出水下成像模型。其次,通过同态滤波对未经过衰减的水下图像进行估计。最后,通过麦克劳林级数对水下成像模型进行级数展开,进而推导出一种保持颜色恒定的水下图像色彩校正模型。实验部分分别对比了水下图像的主观视觉效果和客观评价指标,验证了该算法能够有效地保证水下图像的清晰度和色彩恒定性。校正后的水下图像细节丰富,色彩逼真。     

泡沫图像统计建模与恒常颜色校正算法研究

由于浮选现场的恶劣环境和复杂光照等问题,将导致采集到的泡沫图像不可避免地发生色偏.为了消除以上不利影响,提高后续颜色特征提取的准确性,本文提出了一种基于图像统计建模的泡沫图像恒常颜色校正算法.首先,通过对泡沫图像统计特性的分析,利用Contourlet变换和广义高斯分布函数对图像进行统计建模.其次,选取颜色恒常性标准图像库(Gray-ball)中已知真实光照的标准图像作为训练样本,建立其统计模型参数集,分别选用常用的5种颜色恒常性算法对其进行颜色校正,并以最小角度误差为每幅标准图像标记最佳颜色恒常性算法.最后,利用K最近邻分类算法将待校正的泡沫图像分至对应的恒常算法中,该算法即为原始泡沫图像的最佳恒常颜色校正算法.实验结果证明,该算法能够获得较好的颜色校正效果.     

宏微观信息增强与色彩校正的高效色调映射

目的 色调映射是一种在保持视觉效果基本不变的前提下将高动态范围图像映射到常规低动态显示设备上进行显示的技术。针对现有方法存在细节模糊、边缘光晕及色彩失真等不足,提出一种宏微观信息增强与色彩校正的色调映射新方法。方法 将给定的高动态范围图像映射到HSV(hue, saturation, value)颜色空间,分离亮度信息与色彩信息。基于人类视觉感知机制,在亮度通道构建宏观一致性和微观显著性的亮度感知压缩模型,并进一步通过调节模型缩放因子消除边缘光晕现象。基于颜色恒常性原理,在色度通道构建自适应饱和度偏移模型,融合亮度压缩信息调整图像的饱和度信息,解决色调映射所造成的主观色彩失真问题。结果 实验结果表明,所提算法在结构保真度、自然度和色调映射质量指数等客观评价方面均优于对比色调映射算法,同时主观平均意见值也取得了最高的4.3分（即好—非常好）。结论 宏微观信息增强的亮度感知压缩模型,在确保场景亮度信息不变的情况下,可以有效增强图像纹理细节的完整性和保真性。融合亮度压缩的饱和度偏移模型可以有效解决亮度压缩导致的图像色彩失真等问题。该色调映射算法效率高、通用性强,可广泛应用于图像压缩、生物医学...