联合多种边缘检测算子的无参考质量评价算法

No-reference image quality assessment using joint multiple edge detection

  • 摘要: 提出了一种联合多种边缘检测算子的无参考质量评价算法,同时考虑一阶和二阶边缘算子,避免了单一算子的局限性.该方法首先将彩色图像转换为灰度图像,然后计算灰度图像的梯度,相对梯度以及LOG特征.本文所使用的特征分为两部分,一部分提取相对梯度方向的标准差,另一部分利用条件熵来量化不同特征之间的相似性和相互关系,并且考虑到人眼特性进行多尺度计算,最后使用自适应增强(AdaBoost)神经网络进行训练和预测.在公共数据库LIVE和TID2008上进行实验,结果表明新方法对失真图像的预测评分与主观评分有较高的一致性,能很好地反映图像质量的视觉感知效果,仅使用10维特征,性能优于现有的主流无参考质量评价算法.

     

    Abstract: Before digital images become available to consumers, they usually undergo several stages of processing, which include acquisition, compression, transmission, and presentation. Unfortunately, each stage introduces certain types of distortion, such as white noise, Gaussian blur, and compression distortion, which may degrade the perceptual quality of the final image. Therefore, it is important to design an effective and robust image quality assessment method to automatically evaluate distortions in image quality. Image quality assessment is widely used in image compression, image deblur, image enhancement, and other image processing domains. In general, no-reference image quality assessment methods have profound practical significance and broad application value; hence, it remains the main focus of many researchers. At present, many image quality assessment methods extract features and predict image quality using single edge detection operations such as gradient or local binary pattern. However, it is difficult for a single edge detection operation to represent the whole perceptual quality of distorted images, and hence, their predictions may not be satisfactory. To eliminate the limitations of single edge detection operation, this paper proposes a new no-reference image quality assessment method based on a multiple edge detection operation. The paper considers first-order and second-order derivative information and utilize their similarity to predict image quality. The proposed method first converted color images to grayscale images, and calculated the gradient magnitude (GM), relative gradient magnitude (RM), relative gradient orientation (RO), and Laplacian of Gaussian (LOG) of the grayscale images. The feature vectors extracted from the maps were divided into two parts, where one part was the standard deviation of RO, and the second part utilized conditional entropy to quantify the similarity and relationship of GM, RM, and LOG. The images were naturally multiscale, and distortions affected the image structures across scales. Hence, all features at two scales were extracted:the original image scale and at a reduced resolution (low-pass filtered and down sampled by a factor of 2). Lastly, an AdaBoost back-propagation network was used to train and establish a regression model to predict the image quality. The experiment of the proposed method was performed on two public databases, LIVE and TID2008, and the results show that the score predicted by this new method has a good correlation with the subjective quality score. Moreover, this method can reflect perceptual quality properly using only ten-dimensional feature vectors, and the performance of correlation coefficient can exceed some state-of-the-art no-reference image quality assessment algorithms.

     

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