【作者】 刘科；

【导师】 朱树元；

【作者基本信息】 电子科技大学 ， 信息与通信工程， 2023， 硕士

【摘要】 视觉信息是人类所获取信息的主要来源,图像是视觉信息存储和传播的主要载体。图像数据的广泛应用引起了数据量激增,给存储、传输和使用都造成了困难。对图像进行压缩是降低数据量的有效手段,但压缩会引起失真,影响人类主观视觉体验。因此需要研制高效图像质量评价方法,从而实现人类视觉感受体验变化与图像质量变化之间的统一。图像质量评价方法中的主观质量评价方法的实现过程耗费大量人力物力,且评价结果易受到人类主观因素影响;评价方法中的客观质量评价方法具有代价低、不受主观因素影响和评价结果具有重现性等优点,成为了当前质量评价领域研究的主要方向。本文在研究多种与压缩图像失真有关的特征的基础之上,采用特征融合的方式形成了能够有效用于客观质量评价的特征,应用后产生了良好的效果,其内容及创新性工作主要包括:(1)根据图像压缩块效应和梯度变化的关系,提出了基于梯度方向性变化的无参考图像质量评价方法。研究了图像一阶梯度方向性特征、二阶梯度方向性特征、方向性纹理变化特征与压缩图像梯度变化的关系,以此为基础构建了基于梯度方向性变化的质量评价模型,应用于压缩图像无参考质量评价,根据图像方向性特征变化实现了对图像质量的有效评价。(2)利用图像压缩块效应和图像局部能量分布之间的关系,提出了基于图像块能量分布的无参考图像质量评价方法。研究了图像块能量变化、块边缘特征与图像局部能量之间的关系,利用图像压缩引起的局部质量和能量变化关系构建了基于图像块能量分布的质量评价模型,实现了对压缩图像质量的有效评价。更多还原

【Abstract】 Visual information is the dominant income formation for human.Images are usually used to store and deliver visual information.The wide application of images has induced the dramatically increasing of data,which results in the problems of storing,transmission and application.Compression is the most effective solution to reduce the image data size although it brings distortion which affects the human visual experience.In order to study the relationship between the change of human visual experience and the change of image quality,it is necessary to design efficient image quality assessment method to reasonably evaluate image quality.Image quality assessment methods can be divided into the subjective quality assessment method and the objective quality assessment method.The subjective quality assessment needs lots of participants and resources.However,its assessment results are often affected by the human subjective decision and not satisfied.The objective quality assessment method is implemented with smaller number of resources and not affected by the subjective factors.Meanwhile,its assessment results can be reproduced.Therefore,the objective quality assessment method is widely studied.Based on the study of a variety of features related to compressed image distortion,this thesis uses feature fusion to form features that can be effectively used for objective quality evaluation,and has achieved good results after application.Its contributions include:(1)According to the relationship between the block artifact of the compressed image and the change of image gradient,a new no reference image quality assessment method based on the change of directional gradient was proposed.To implement this method,the first-order directional gradient,the second-order directional gradient and the directional change of the image were studied.These features were fused together and then used to construct a quality assessment model which achieves a high assessment efficiency for the compressed images.(2)According to the relationship between the block artifact of image compression and the local energy distribution,an energy distribution-based no reference image quality assessment method was proposed.In this method,the relationship between image block energy change and block edge feature was studied,which is used to guide the construction of the quality assessment model based on the change of image block energy distribution.With this proposed method,an accurate quality assessment for the compressed images is also achieved.更多还原