一种基于颜色视觉敏感度的特征提取算法

特征选择技术对于图像检索系统有效实现相关目标的识别具有重要的意义.依据视觉生理学和视觉心理学关于不同颜色间存在敏感度差异的理论,并利用Stevens法则和HSV颜色空间的六棱锥模型,提出了一种构造颜色敏感度函数的算法.新算法以主观信息量多少为评价标准,通过系数补偿,实现了显著程度不同颜色间特征幅值的平衡,从而提高了检索特征与感知特征的一致性.实验结果证明了新算法能够稳定、有效地提升图像检索系统的性能.     

一种多视点视频颜色校正方法

针对多视点视频系统中不同视点视频间存在的颜色差异,提出了一种RGB空间下的颜色校正方法.以与真实世界颜色比较接近的视频作为参考视频,对存在颜色差异的视频进行颜色校正,首先将两个视频同一时刻的一帧图像从YUV空间变换到RGB空间,计算图像r,g,b三通道的校正系数,然后对三通道颜色进行校正,最后将校正后的RGB数据变换回...     

基于颜色校正的水下照明图像融合方法

针对水下照明图像存在不均匀色偏、对比度低和细节模糊等问题，提出了一种基于颜色校正的水下照明图像融合方法。首先利用图像通道间的像素相关性，对红通道进行补偿；然后基于颜色校正图像，利用非线性反锐化掩蔽（Nonlinear unsharp masking）技术获得锐度增强图像，采用具有瑞利分布的限制直方图获得全局拉伸图；最后通过多尺度融合策略生成融合图像。在自建数据集（Real underwater lighting image,RULI）上的实验结果表明：本文方法能够去除混合光照在成像过程中的不均匀散射干扰，并大幅度提高图像的细节清晰度。其图像质量评估指标（Underwater image quality measures,UIQM）和（Image entropy,IE）的平均值分别为4.7399和7.7617，优于现有文献涉及的相关算法。     

一种基于直方图匹配的立体视频颜色校正算法

针对立体视频序列视点间颜色不一致的问题,实现基于直方图匹配的立体视频颜色校正算法。深入分析视点图像间颜色存在的乘性和加性差异,结合颜色差异建模,使用直方图匹配算法校正颜色误差。实验结果表明,本文实现的颜色校正算法计算复杂度较低,并且在保持图像视觉效果的同时,能较好的消除参考图像与目标图像之间的颜色差异,是一种有效的立体视频图像颜色校正算法。     

基于多尺度区域的图像颜色校正算法

图像颜色校正是多摄像机视觉应用中的一项重要技术。本文提出了一种基于多尺度区域的局部颜色校正算法,主要思想是在参考图像与待校正图像之间建立特征点的对应关系。此算法根据尺度不同的区域内可获得的对应特征点数目不同的特性,在不同尺寸参数对待校正图像进行分割,以得到稳定的特征点对应,进而获取准确的颜色校正信息,提高了颜色校正的准确性和鲁棒性。此外,本文还考虑了局部校正对图像颜色一致性减弱的问题,进行了平滑处理。实验证明,本文所提出的方法能获得较好的校正结果。     

一种处理多光谱彩色合成图像的白平衡法

多光谱彩色合成图像是直接提取多光谱图像中的R、G、B波段合成的彩色图像.但由于多光谱成像探测器光谱响应性能的差异,造成合成的彩色图像偏色严重,为了重现真实色彩,需进行颜色校正.针对目前传统白平衡法与色度学合成法的不足,提出了一种基于光谱信息的改进白平衡法,用于多光谱彩色合成图像的颜色校正.经实验验证,该方法不仅实现简单,校正过程中不需要标准真彩色图像,也不需要预测图像中所有地物的光谱反射率,而且改进了传统算法,获得的图像更为真实.     

结合特征融合与物理校正的水下图像增强方法

为解决由于光的吸收和散射现象导致拍摄的水下图像呈现出严重色偏，对比度低等质量问题，本文提出轻量级特征融合网络和多颜色模型校正相结合的水下图像增强方法。首先使用自构建块代替卷积层的编码器和解码器结构的特征融合网络对水下图像色偏进行校正，网络中改进的特征融合模块降低全连接层对图像空间结构的破坏，保护空间特征，减少模块的参数量。同时改进的注意力模块并行池化计算提取特征图纹理细节且保护背景信息。然后使用多颜色模型校正模块根据像素之间关系进行校正，进一步减少色偏，提高对比度和亮度。实验结果表明，与最新的图像增强方法对比，在有参考图像数据集上，本文方法的NRMSE、PSNR和SSIM评价指标的平均值分别比第二名提升了9.3%、3.7%和2.3%。在无参考图像数据集上，本文方法的UCIQE、IE和NIQE评价指标的平均值比第二名提升了6.0%、2.9%和4.5%。综合主观感知和客观评价，本文方法能校正水下图像色偏，提升对比度和亮度，提高图像质量。     

基于暗通道和伽马变换的水下图像增强

光在水下传播存在吸收和散射现象,导致水下图像颜色失真、对比度低.为此,提出了一种基于暗通道先验和伽马变换的水下图像增强算法.首先,在RGB空间利用暗通道先验估计水下图像透射率和大气光照值,加权处理后得到自适应补偿参数,进而对图像颜色校正.在此基础上,将增强后的RGB图像转化到HSV颜色空间,对V通道进行自适应伽马变换,提高图像的对比度.最后,在公用水下图像增强数据集(RUIE)上进行实验,并与现有增强算法进行比较.实验结果表明,所提算法显著提高了水下图像的视觉质量,优于其他相关算法.     

不同颜色空间多视点视频颜色校正的性能分析

在简述几种颜色空间及多视点视频线性颜色校正方法的基础上,利用多视点视频线性颜色校正方法对不同序列分别在3个颜色空间(CIELab,RGB,YUV)中进行校正,从客观的视差平均值计算和主观评价质量两个方面对校正效果进行比较.实验结果表明,序列两视点所在的空间中的直图表述差异越大,则在此空间中进行颜色校正的效果越好.     

融合颜色特征和对比度特征的图像显著性检测

图像显著性检测能够获取一幅图像的视觉显著性区域,是计算机视觉的研究热点之一。提出一种结合颜色特征和对比度特征的图像显著性检测方法。首先构造图像在HSV空间的颜色函数以获取图像颜色特征;然后使用SLIC超像素分割算法对图像进行预处理,基于超像素块的对比度特征计算图像显著性;最后将融合颜色特征和对比度特征的显著图经过导向滤波优化形成最终的显著图。使用本文算法在公开数据集MSRA-1000上进行图像显著性检测,并与其他6种算法进行比较。实验结果表明本文算法结合了图像像素点和像素块的信息,检测的图像显著性区域轮廓更加完整,优于其他方法。     

Objective color image quality assessment based on Sobel magnitude

Image quality assessment algorithms aim to evaluate the perceptual quality of an image by assigning an evaluation score. By comparing the scores, the perceptual similarity or difference between two images can be assessed. In this paper, we present a new full-reference image quality metric method which was developed by combining Sobel magnitude and chrominance information in the YIQ color space. But differing from existing methods, our model incorporates color intensity adaptation to extract and enhance perceptually significant image features. The proposed metrics are tested on three well-known databases available in the literature (TID2013, TID2008, and CSIQ). Experimental results presented to confirm that the proposed metric is an effective and have low computational complexity.     

典型场景彩色融合图像颜色协调性的主观评价

彩色夜视技术是当前夜视技术发展的前沿,但如何实现对彩色夜视图像质量的客观评价仍然是当前困扰人们的问题.针对北京理工大学高绍姝提出的颜色协调性模型主观评价实验人数不足的问题,按照国际视觉实验标准重新设计并进行了颜色协调性的主观视觉评价实验,主观评价测试的彩色融合图像分成绿色植物、海天和城镇建筑物三类典型场景,主观实验人数提高到52人;对主观评价实验结果的回归分析结果表明:高绍姝提出的颜色协调性评价模型在三类场景与主观评价结果均具有较好的一致性,明显优于其他评价模型,可以有效地对不同场景彩色融合图像的颜色协调性进行客观评价.     

A no-reference perceptual image quality assessment database for learned image codecs

The drastic growth of research in image compression, especially deep learning-based image compression techniques, poses new challenges to objective image quality assessment (IQA). Typical artifacts encountered in the emerging image codecs are significantly different from that produced by traditional block-based codecs, leading to inapplicability of the existing objective IQA algorithms. Towards advancing the development of objective IQA algorithms for recent compression artifacts, we built a learning-based compressed image quality assessment (LCIQA) database involving traditional block-based image codecs, hybrid neural network based image codecs, convolutional neural network based and generative adversarial network (GAN) based end-to-end optimized image coding approaches. Our study confirms the statistical difference and human perception difference between reconstructions of learned compression and traditional block-based compression. We propose a two-step deep learning model for learning-based compressed image quality assessment. Extensive experiments on LCIQA database demonstrate that our proposed model performs better than other counterparts on learning-based compressed images, especially on GAN compressed images, and achieves competitive performance to the state-of-the-art IQA metrics on traditional compressed images.     

Image quality assessment based on Prewitt magnitude

The goal of image quality assessment (IQA) research is to use computational models to calculate the quality of images consistently with subjective evaluations. In this paper, we propose a new image quality assessment (IQA) algorithm by combining Prewitt magnitude and regional mutual information (RMI) in HSV color space. The Prewitt operator is usually used for edge detection and can extract vertical edge more accurately than other operators. The HSV color space encapsulates information about a color in terms that are more natural and intuitive to humans. The proposed method PMRMI first transforms reference and distorted images from RGB color space into HSV color space and Prewitt magnitude is introduced to extract key edge features of each channel. Then the regional mutual information is calculated to measure the similarity of the two images. After that, a weighting method is utilized for better consistency with subjective evaluations. Therefore we get a single quality score. Experiments on various image distortion types demonstrate that the proposed algorithm can achieve better consistency with the subjective evaluations than PSNR and SSIM.     

Spatial pooling for measuring color printing quality attributes

Many objective image quality assessment algorithms firstly apply quality metrics in local regions that results in a quality map, and then pool the quality values in the quality map into a single quality score. The simplest pooling method is the average of quality values, which assumes that all the quality values are independent and equally important. However, visual perception is so complex that the assumption underlying average pooling might be too strict. There is an agreement that some regions in the images might be more perceptually significant, which leads to more advanced spatial pooling methods. In this work we evaluate existing spatial pooling methods for five important quality attributes, which are proposed to reduce the complexity of image quality assessment. The results show that: (1) more advanced spatial pooling methods are generally better than simple average; (2) spatial pooling depends on both image quality metrics and the attributes of the image.     

夜视融合图像质量客观评价方法

为建立通用、客观的融合图像质量评价方法，在分析图像质量评价与融合图像质量评价关系基础上，给出了图像质量评价与融合图像质量评价的一般表达式。依据信息理论和结构相似度评价方法，对建立的4种客观评价指标，采用4种融合方法获得的36幅融合图像进行了主观评价实验，统计分析结果显示，结合人类视觉系统的客观评价方法优于熵、交互信息量等评价指标，但仍未达到高度的主客观一致性，说明构建通用、高效、主客观一致性好的融合图像质量评价指标存在较大难度，同时对可能存在的原因进行了分析。     

Ambiguity of objective image quality metrics: A new methodology for performance evaluation

Objective image quality metrics try to estimate the perceptual quality of the given image by considering the characteristics of the human visual system. However, it is possible that the metrics produce different quality scores even for two images that are perceptually indistinguishable by human viewers, which have not been considered in the existing studies related to objective quality assessment. In this paper, we address the issue of ambiguity of objective image quality assessment. We propose an approach to obtain an ambiguity interval of an objective metric, within which the quality score difference is not perceptually significant. In particular, we use the visual difference predictor, which can consider viewing conditions that are important for visual quality perception. In order to demonstrate the usefulness of the proposed approach, we conduct experiments with 33 state-of-the-art image quality metrics in the viewpoint of their accuracy and ambiguity for three image quality databases. The results show that the ambiguity intervals can be applied as an additional figure of merit when conventional performance measurement does not determine superiority between the metrics. The effect of the viewing distance on the ambiguity interval is also shown.     

基于边缘特征和亮度的彩色图像质量评价

传统的图像质量评价算法大多针对灰度图像而言,这些算法利用图像中对应的像素灰度误差建立数学模型来评价图像,不能够评价彩色图像的质量。本文提出了一种基于边缘特征和颜色亮度信息的彩色图像质量评价方法。首先,利用Sobel算子提取图像边缘;其次,定义了边缘和亮度相似系数来分析它们对图像的影响。最后,综合考虑这两个因素建立数学模型对彩色图像进行评价。大量实验表明:该方法适合评价彩色图像;同时,该实验结果与人的主观感觉的一致性较好。     

Objective and subjective evaluation of High Dynamic Range video compression

A number of High Dynamic Range (HDR) video compression algorithms proposed to date have either been developed in isolation or only-partially compared with each other. Previous evaluations were conducted using quality assessment error metrics, which for the most part were developed for qualitative assessment of Low Dynamic Range (LDR) videos. This paper presents a comprehensive objective and subjective evaluation conducted with six published HDR video compression algorithms. The objective evaluation was undertaken on a large set of 39 HDR video sequences using seven numerical error metrics namely: PSNR, logPSNR, puPSNR, puSSIM, Weber MSE, HDR-VDP and HDR-VQM. The subjective evaluation involved six short-listed sequences and two ranking-based subjective experiments with hidden reference at two different output bitrates with 32 participants each, who were tasked to rank distorted HDR video footage compared to an uncompressed version of the same footage. Results suggest a strong correlation between the objective and subjective evaluation. Also, non-backward compatible compression algorithms appear to perform better at lower output bit rates than backward compatible algorithms across the settings used in this evaluation.