No-reference image quality assessment based on sparse representation

We present a no-reference (NR) image quality assessment (IQA) algorithm that is inspired by the representation of visual scenes in the primary visual cortex of the human visual system. Specifically, we use the sparse coding model of the area V1 to construct an overcomplete dictionary for sparsely representing pristine (undistorted) natural images. First, we empirically demonstrate that the distribution of the sparse representation coefficients of natural images have sharp peaks and heavy tails, and can therefore be modeled using a Univariate Generalized Gaussian Distribution (UGGD). We then show that the UGGD model parameters form good features for distortion estimation and formulate our no-reference IQA algorithm based on this observation. Subsequently, we find UGGD model parameters that are representative of the class of pristine natural images. This is achieved using a training set of undistorted natural images. The perceptual quality of a test image is then defined to be the likelihood of its sparse coefficients being generated from the pristine UGGD model. We show that the proposed algorithm correlates well with subjective evaluation over several standard image databases. Further, the proposed method allows us to construct a distortion map that has several useful applications like distortion localization, adaptive rate allocation etc. Finally and importantly, the proposed NR-IQA algorithm does not make use of any distortion information or subjective scores during the training process.

Quality assessment of images with multiple distortions based on phase congruency and gradient magnitude

In practice, images available to consumers usually undergo several stages of processing including acquisition, compression, transmission, and presentation, and each stage may introduce certain type of distortion. It is common that images are simultaneously distorted by multiple types of distortions. Most existing objective image quality assessment (IQA) methods have been designed to estimate perceived quality of images corrupted by a single image processing stage. In this letter, we propose a no-reference (NR) IQA method to predict the visual quality of multiply-distorted images based on structural degradation. In the proposed method, a novel structural feature is extracted as the gradient-weighted histogram of local binary pattern (LBP) calculated on the gradient map (GWH-GLBP), which is effective to describe the complex degradation pattern introduced by multiple distortions. Extensive experiments conducted on two public multiply-distorted image databases have demonstrated that the proposed GWH-GLBP metric compares favorably with existing full-reference and NR IQA methods in terms of high accordance with human subjective ratings.

In this paper, we propose a new standard haze image database with nearly all kinds of haze situations. Our database includes haze-free images as well as different levels and situations of haze images, such as snowy and extremely serious haze images. Our database also records the related weather and air quality information. Moreover, the database offers a mean opinion score (MOS) for each image as the subjective evaluation of the haze severity. Our database provides ample haze images with various objective and subjective descriptions, and has significantly potential scientific value. Since haze is a reason leading to the degradation of the image quality, obtaining the quality of haze images is also necessary and meaningful. In this paper, a novel no-reference image quality assessment (IQA) method for haze images is also proposed. Our method analyzes the model of haze images to evaluate the quality. The experimental results on the haze database show that our method is consistent with the subjective evaluation.

High Dynamic Range (HDR) imaging captures a wider range of luminance and color than Standard Dynamic Range (SDR), enabling more faithful representations of real-world scenes. Since most displays only support SDR, HDR content must be converted to SDR, often resulting in perceptual distortions like unnatural contrast, loss of detail or color artifacts. This paper evaluates No-Reference Image Quality Assessment (NR-IQA) methods on SDR images derived from HDR using the ESPL-LIVE HDR Image Database, which includes tone-mapped images and images created by multi-exposure fusion, together with associated mean opinion scores (MOS) and standard deviations, providing a reliable ground truth for evaluation. Seven NR-IQA methods, both traditional and Deep Learning (DL)-based, were tested and compared. DL algorithms performed best, with prediction errors below the standard deviation of MOS. Despite moderate correlation values (around 0.5), the results demonstrate the potential of these methods for practical image quality monitoring.

No-reference image quality assessment in contourlet domain

No-reference image quality assessment (NR-IQA), which aims to predict image quality without accessing to reference images, is a fundamental and challenging problem in the field of image processing. Nevertheless, there are few researches about contrast-distorted images and results of the existing NR-IQA methods which cannot be in accordance with the subjective assessment results further. Therefore, an effective NR-IQA method for contrast-distorted image is proposed in this paper. Firstly, the proposed method extracts five features of all images from the database based on the natural scene statistics (NSS) model. Then the curve fitting method is subsequently represented to calculate values of natural image features. Finally, an improved Support Vector Regression (SVR) learning method based on grid search is proposed to establish the mapping between image feature values and the quality score of a test image. Experiments proved that the proposed method is effective when compared with other related state-of-the-art image quality assessment (IQA) methods based on three standard databases.

No-reference image quality assessment for photographic images based on robust statistics

No-reference image quality assessment based on spatial and spectral entropies

Faithful measurement of perceptual quality is of significant importance to various multimedia applications. By fully utilizing reference images, full-reference image quality assessment (FR-IQA) methods usually achieves better prediction performance. On the other hand, no-reference image quality assessment (NR-IQA), also known as blind image quality assessment (BIQA), which does not consider the reference image, makes it a challenging but important task. Previous NR-IQA methods have focused on spatial measures at the expense of information in the available frequency bands. In this paper, we present a multiscale deep blind image quality assessment method (BIQA, M.D.) with spatial optimal-scale filtering analysis. Motivated by the multi-channel behavior of the human visual system and contrast sensitivity function, we decompose an image into a number of spatial frequency bands by multiscale filtering and extract features for mapping an image to its subjective quality score by applying convolutional neural network. Experimental results show that BIQA, M.D. compares well with existing NR-IQA methods and generalizes well across datasets.

An optimized CNN-based quality assessment model for screen content image

The current rate of success in launching satellites and advances in onboard and ground image processing have led to a dramatic increase in the scale of remote sensing image data. This has resulted in considerable research on how to provide the best quality of experience to end users. However, subjective image quality assessment (IQA) is time-consuming, cumbersome, expensive and cannot be implemented automatically using computers. Thus, subjective IQA may not be suitable for application requirements. In this paper, we design and construct a usability-based subjective remote sensing IQA database. A corresponding no-reference IQA method is also proposed. The new IQA method uses scale-invariant feature transforms to form a dictionary and then a support vector machine to obtain an IQA model. The experimental results show that the new subjective IQA database is highly suited to the task, and the quality predictions of the new IQA method correlate well with human subjective scores in the new database.

In recent years, deep learning has achieved significant progress in many respects. However, unlike other research fields with millions of labeled data such as image recognition, only several thousand labeled images are available in image quality assessment (IQA) field for deep learning, which heavily hinders the development and application for IQA. To tackle this problem, in this paper, we proposed an error self-learning semi-supervised method for no-reference (NR) IQA (ESSIQA), which is based on deep learning. We employed an advanced full reference (FR) IQA method to expand databases and supervise the training of network. In addition, the network outputs of expanding images were used as proxy labels replacing errors between subjective scores and objective scores to achieve error self-learning. Two weights of error back propagation were designed to reduce the impact of inaccurate outputs. The experimental results show that the proposed method yielded comparative effect.

Objective quality assessment metrics that are consistent with human judgments of image quality, play an important role in many image processing applications. No-reference image quality assessment (NR-IQA) algorithms evaluate the quality of distorted images without any information about the reference images. In this paper, we propose an accurate and simple method for NR-IQA. In this method local binary pattern (LBP) operator is first applied to subbands of wavelet decomposed image separately; then histogram of LBP codes is calculated and concatenated to form quality aware features. Finally, support vector regression (SVR) is utilized to map the feature vectors to subjective quality scores. The experimental results for LIVE and TID2008 databases show that our proposed method is highly correlated to the subjective scores, and competitive to state-of-the-art NR-IQA methods.

The automatic assessment of perceived image quality is crucial in the field of image processing. To achieve this idea, we propose an image quality assessment (IQA) method for blurriness. The features of gradient and singular value were extracted in this method instead of the single feature in the traditional IQA algorithms. According to the insufficient size of existing public image quality assessment datasets to support deep learning, machine learning was introduced to fuse the features of multiple domains, and a new no-reference (NR) IQA method for blurriness denoted Feature fusion IQA(Ffu-IQA) was proposed. The Ffu-IQA uses a probabilistic model to estimate the probability of each edge detection blur in the image, and then uses machine learning to aggregate the probability information to obtain the edge quality score. After that uses the singular value obtained by singular value decomposition of the image matrix to calculate the singular value score. Finally, machine learning pooling is used to obtain the true quality score. Ffu-IQA achieves PLCC scores of 0.9570 and 0.9616 on CSIQ and TID2013, respectively, and SROCC scores of 0.9380 and 0.9531, which are better than most traditional image quality assessment methods for blurriness.