No-reference image contrast measure using image statistics and random forest

Multimedia Tools and Applications - Image quality assessment is very crucial for certain image processing applications. Images can be distorted from multiple sources like a fault in sensors, camera...     

基于双变换的红外与可见光图像融合增强

通过研究可见光视觉图像与红外图像序列的相关特性及融合处理中存在的问题, 提出一种基于视觉图像预增强处理的曲波与小波双变换融合机制来有效保留边缘信息和图像细节信息。实验结果表明所提出的方法提高了融合图像的视觉感知质量, 为遮挡和伪装目标的检测和定位提供了更为有效的空间环境, 并且融合增强后的图像具有更高的信噪比和更少的人工痕迹, 与当前最新的其他方法相比是一种具有更好融合质量和更高效率的图像/视频融合方法。     

用于实现图像对比度增强的可逆数据隐藏算法

针对已有算法嵌入率低、算法过程复杂等问题,提出一种新的可逆数据隐藏算法。算法为了提高信息隐藏率,首先选取直方图中值点两侧的峰值进行数据嵌入。在多次嵌入之后,算法选择中值点位置嵌入所有峰值信息,由于中值点在嵌入后可以直接定位,因此可以实现可逆嵌入与恢复,从而不需要已有算法最低有效位的替换过程,减少了算法过程的复杂性。算法在两个图像集上进行性能测试,先与已有算法进行数据嵌入量比较,接着与MATLAB中3个对比度增强函数进行比较,用于评估算法的嵌入容量以及对比度增强后的图像质量。实验结果表明,所提算法在实现可逆数据隐藏和对比度增强的同时,嵌入容量有较大的提高。     

A new image contrast enhancement technique based on a contrast discrimination model

A new image contrast enhancement technique is presented. It is based on experimental studies of contrast discrimination of objects in a background of variable brightness. A mathematical model that follows a power law has been developed. Comparisons between the proposed technique and both of the histogram equalization and histogram hyperbolization techniques have been made. Tests on different images show that the new method presents better results.     

微粒群优化和视觉感应相结合的图像增强方法

对粒群优化算法进行了改进,提出了一种微粒群优化和视觉感应相结合的图像增强方法,通过微粒群算法优化灰度图像的平均明暗信息熵差值,自适应地选择图像灰度转换函数,用以实现图像的增强。该方法不仅参数个数少,优化速度快,在搜索能力上优于粒群优化算法,而且能够保证算法的全局收敛性。仿真实例证明了该方法在图像增强上的有效性和优越性。     

基于人眼视觉特性的红外图像细节增强

由于红外成像的机理和探测器的限制,使得红外图像具有对比度低以及边缘模糊的特点。导致红外图像不适合被人眼及机器观察。传统的红外图像增强方法由于没有考虑人眼的因素,导致仍然不适合被人眼观察。本文结合分层思想提出一种基于人眼视觉的红外图像细节的增强的方法。该方法首先利用双边滤波器将图像分成包含图像低频概貌信息的基础层和包含图像高频细节信息的细节层。基础层的处理是运用人眼视觉特性的方法将其映射到显示器可显示范围内。细节层的处理是应用了自适应增益的方法对细节层进行增强。最后将两层的处理结果进行合并量化到8-bit范围内。采用大量的红外图像对算法进行测试,实验结果表明本算法能够改善红外图像对比度低和边缘模糊的缺点。     

Segment dependent dynamic multi-histogram equalization for image contrast enhancement

Histogram equalization (HE) method proved to be a simple and most effective technique for contrast enhancement of digital images. However it does not preserve the brightness and natural appearance of the images, which is a major drawback. To overcome this limitation, several Bi- and Multi-HE methods have been proposed. Although the Bi-HE methods significantly enhance the contrast and may preserve the brightness, the natural appearance of the images is not preserved as these methods suffer with the problem of intensity saturation. While Multi-HE methods are proposed to further maintain the brightness and natural appearance of images, but at the cost of contrast enhancement. In this paper, two novel Multi-HE methods for contrast enhancement of natural images, while preserving the brightness and natural appearance of the images, have been proposed. The technique involves decomposing the histogram of an input image into multiple segments based on mean or median values as thresholds. The narrow range segments are identified and are allocated full dynamic range before applying HE to each segment independently. Finally the combined equalized histogram is normalized to avoid the saturation of intensities and un-even distribution of bins. Simulation results show that, for the variety of test images (120 images) the proposed method enhances contrast while preserving brightness and natural appearance and outperforms contemporary methods both qualitatively and quantitatively. The statistical consistency of results has also been verified through ANOVA statistical tool.     

Multichannel image contrast enhancement based on linguistic rule-based intensificators

This study follows the direct approach to image contrast enhancement, which changes the image contrast at each its pixel and is more effective than the indirect approach that deals with image histograms. However, there are only few studies following the direct approach because, by its nature, it is very complex. Additionally, it is difficult to develop an effective method since it is required to keep a balance in maintaining local and global image features while changing the contrast at each individual pixel. Moreover, raw images obtained from many sources randomly influenced by many external factors can be considered as fuzzy uncertain data. In this context, we propose a novel method to apply and immediately handle expert fuzzy linguistic knowledge of image contrast enhancement to simulate human capability in using natural language. The formalism developed in the study is based on hedge algebras considered as a theory, which can immediately handle linguistic words of variables. This allows the proposed method to produce an image contrast intensificator from a given expert linguistic rule base. A technique to preserve global as well as local image features is proposed based on a fuzzy clustering method, which is applied for the first time in this field to reveal region image features of raw images. The projections of the obtained clusters on each channel are suitably aggregated to produce a new channel image considered as input of the pixelwise defined operators proposed in this study. Many experiments are performed to demonstrate the effect of the proposed method versus the counterparts considered.     

基于PCNN与LR的低对比度图像增强方法

图像增强是指对图像进行加工,以获得更“好”的视觉效果的一种图像处理技术。由于图像的最终接收者是人,所以评价图像“好坏”的关键在于其是否符合人类视觉系统的特性。针对低对比度图像,结合人眼视觉神经系统的感知特性,提出了一种基于PCNN与LR模型的图像增强方法。分析和仿真结果表明,该法能够较好地突出图像的边缘细节信息,明显地改善图像的视觉效果。     

基于人眼视觉特性的彩色图像增强算法

在分析现有彩色图像增强算法的基础上,按照视觉心理感知特性选择HSV色彩空间,并在此空间提出了新的彩色图像增强算法,保持色调不变,从而保证了没有颜色的失真或偏移。实验证明,经本文算法增强后的彩色图像画面更清晰、层次感更强、色彩也更加丰富,达到了预期的目的。     

基于人眼视觉感知驱动的井下图像增强算法

为解决传统的对比度增强方法在对井下图像进行处理时不能兼顾压缩动态范围、调整亮度以及增强图像对比度等问题,提出一种基于人眼视觉感知特性的井下图像对比度增强算法。首先根据人眼亮度掩蔽特性对图像进行区域划分,然后基于非线性亮度映射模型,对图像的不同区域进行不同尺度的非线性调整,最后再将亮度调整后的不同区域组合成新的图像。实验结果表明,该方法能有效增强井下低照度图像的对比度,提升图像的视觉效果。     

A fuzzy histogram weighting method for efficient image contrast enhancement

Multimedia Tools and Applications - Image contrast enhancement is an important step in digital image processing applications. In this paper, we present an efficient contrast enhancement approach,...     

Some algorithms for image enhancement incorporating human visual response

Any image processing technique which is used to improve the appearance of an image for human perception or machine analysis should incorporate the characteristics of the human visual system. One of the major characteristics of the human visual system is the logarithmic response to light intensity, which we have attempted to include in this paper. Some new algorithms for image enhancement, edge detection and smoothing have been described and their results are presented. Only the edge detection technique is space-variant. All the techniques are simple and economical, and can be supplied to each pixel in parallel.     

基于视觉特性的彩色图像增强算法研究

为了对彩色图像进行分析和识别,在深入分析HSV彩色模型的基础上,提出了一种新的彩色图像增强算法.该方法利用像素点邻域的均值和方差对HSV模型的亮度分量增强,在获得图像细节的同时保持图像缓慢变化的部分;根据亮度分量的变化情况,利用亮度和饱和度之间的相关系数,对HSV模型的饱和度分量进行调整.通过对图像进行主观分析和客观分析,该种算法不仅拉伸了图像的对比度,增加了图像的清晰度,而且图像色彩丰富,更加符合人的视觉特性.     

一种基于雾天图像增强的SURF图像匹配方法

在地质灾害监测系统中,可以通过图像的变化检测对发生的灾害进行监测。要精确地进行变化检测,需要首先对图像进行匹配。针对雾天图像匹配精度低的问题,提出了一种基于雾天图像增强的SURF（Speed Up Robust Feature）图像匹配方法,有效地提高了雾天图像的匹配精度。用MSR（Multi Scale Retinex）算法对雾天图像进行增强处理,采用SURF算法完成特征点的提取,用欧式距离来度量特征点的相似度,根据相似三角形的距离比例不变性删除误匹配的点对。实验结果表明,该方法显著提高了图像特征点的匹配精度,为后续利用图像变化检测进行灾害监测提供了良好的基础。     

Artificial neural network visual model for image quality enhancement

An artificial neural network visual model is developed, which extracts multi-scale edge features from the decompressed image and uses these visual features as input to estimate and compensate for the coding distortions. This provides a generic postprocessing technique that can be applied to all the main coding methods. Experimental results involving postprocessing of the JPEG and quadtree coding systems show that the proposed artificial neural network visual model significantly enhances the quality of reconstructed images, both in terms of the objective peak signal-to-noise ratio and subjective visual assessment.     

基于第二代Curvelet变换的低对比度图像增强

针对传统图像增强方法用于低对比度图像时,存在对噪声敏感、局部过增强等问题,提出了一种基于第二代 Curvelet 变换的增强方法。将图像进行多尺度多方向的 Curvelet 变换;引入分段非线性函数的思想,调整低频子带系数,提高图像整体的对比度;对各尺度的高频子带系数进行非线性加权,增强图像细节,并进行阈值降噪。实验表明,该方法优于常用的空间域直方图均衡化和小波域图像增强法,能有效地提高图像的对比度、降低噪声,并且较好地保留边缘信息,具有良好的视觉效果。     

基于对比度受限自适应直方图均衡的乳腺图像增强

采用对比度受限自适应直方图均衡对乳腺图像进行增强,有效地增强了乳腺图像中的细节,如钙化点、乳导管等组织;并通过对算法中相关参数研究,得到应用于乳腺图像增强的参数优选值,以求获得较好的增强效果,为医师分析影像提供方便。通过与灰度直方图均衡的结果进行比较得出：对比度受限自适应直方图均衡为乳腺数字图像增强的有效方法,在计算机辅助乳腺诊断方面有较高应用价值。