Visual Quality Measures Research Articles

HOS-based image sequence noise removal

In this paper, a new spatiotemporal filtering scheme is described for noise reduction in video sequences. For this purpose, the scheme processes each group of three consecutive sequence frames in two steps: 1) estimate motion between frames and 2) use motion vectors to get the final denoised current frame. A family of adaptive spatiotemporal L-filters is applied. A recursive implementation of these filters is used and compared with its nonrecursive counterpart. The motion trajectories are obtained recursively by a region-recursive estimation method. Both motion parameters and filter weights are computed by minimizing the kurtosis of error instead of mean squared error. Using the kurtosis in the algorithms adaptation is appropriate in the presence of mixed and impulsive noises. The filter performance is evaluated by considering different types of video sequences. Simulations show marked improvement in visual quality and SNRI measures cost as well as compared to those reported in literature.

Harmonic postprocessing to conceal for transmission errors in DWT transmitted images

The discrete wavelet transform has become a dominant method in transform coding, but transmission of the resulting coefficients has lacked efficient postprocessing to recover from block loss in the lowest frequency wavelet subband. This paper relates the lost coefficients to the surrounding valid ones by the Laplace equation on a square grid. The properties of its solutions, viz. harmonic functions, ensure uniform and stable performance of the recovery scheme. The method is compared with interpolative functions already used for block loss recovery, such as the bicubic Coons surface (the only reported method to recover lowest frequency subband block loss) and NURBS, used in DCT domain block loss recovery. Experiments on standard test images show uniform superiority in both visual quality and PSNR measurement. The method can reconstruct both coefficients in the wavelet domain and pixels in the image domain. We compare results experimentally and analytically, to guide practical application.

Image information and visual quality

Measurement of visual quality is of fundamental importance to numerous image and video processing applications. The goal of quality assessment (QA) research is to design algorithms that can automatically assess the quality of images or videos in a perceptually consistent manner. Image QA algorithms generally interpret image quality as fidelity or similarity with a "reference" or "perfect" image in some perceptual space. Such "full-reference" QA methods attempt to achieve consistency in quality prediction by modeling salient physiological and psychovisual features of the human visual system (HVS), or by signal fidelity measures. In this paper, we approach the image QA problem as an information fidelity problem. Specifically, we propose to quantify the loss of image information to the distortion process and explore the relationship between image information and visual quality. QA systems are invariably involved with judging the visual quality of "natural" images and videos that are meant for "human consumption." Researchers have developed sophisticated models to capture the statistics of such natural signals. Using these models, we previously presented an information fidelity criterion for image QA that related image quality with the amount of information shared between a reference and a distorted image. In this paper, we propose an image information measure that quantifies the information that is present in the reference image and how much of this reference information can be extracted from the distorted image. Combining these two quantities, we propose a visual information fidelity measure for image QA. We validate the performance of our algorithm with an extensive subjective study involving 779 images and show that our method outperforms recent state-of-the-art image QA algorithms by a sizeable margin in our simulations. The code and the data from the subjective study are available at the LIVE website.

Image Format for Spectral Image Browsing

The technology for spectral imaging has developed rapidly during the past few years. The spectral cameras are usable in a variety of applications. These applications include archiving of artistic and museum objects, telemedicine, and e-commerce. In all of these applications, a large number of images will be stored in the archives with a high spatial and spectral (color) resolution. A possibility for fast browsing of these archives is needed. For browsing, the speed is more important than the high resolution of the images. The original, high resolution spectral images should be kept in the archive. In this paper, the authors present a new spectral image browsing architecture. This architecture contains a new data structure for spectral images. The data structure is based on a low-dimensional representation of original spectral images including a spatial subsampling of eigenimages. The authors show that this format enables fast network transfer of spectral images with a small loss of spatial and spectral information. Also, measures of visual quality are given.

An information fidelity criterion for image quality assessment using natural scene statistics

Measurement of visual quality is of fundamental importance to numerous image and video processing applications. The goal of quality assessment (QA) research is to design algorithms that can automatically assess the quality of images or videos in a perceptually consistent manner. Traditionally, image QA algorithms interpret image quality as fidelity or similarity with a "reference" or "perfecft" image in some perceptual space. Such "full-referenc" QA methods attempt to achieve consistency in quality prediction by modeling salient physiological and psychovisual features of the human visual system (HVS), or by arbitrary signal fidelity criteria. In this paper, we approach the problem of image QA by proposing a novel information fidelity criterion that is based on natural scene statistics. QA systems are invariably involved with judging the visual quality of images and videos that are meant for "human consumption." Researchers have developed sophisticated models to capture the statistics of natural signals, that is, pictures and videos of the visual environment. Using these statistical models in an information-theoretic setting, we derive a novel QA algorithm that provides clear advantages over the traditional approaches. In particular, it is parameterless and outperforms current methods in our testing. We validate the performance of our algorithm with an extensive subjective study involving 779 images. We also show that, although our approach distinctly departs from traditional HVS-based methods, it is functionally similar to them under certain conditions, yet it outperforms them due to improved modeling. The code and the data from the subjective study are available at.

Visual Quality Measures for Characterizing Planar Robot Grasps

This paper presents and analyzes 12 quality measures that characterize robotic grips according to their stability and reliability. The measures are designed to assess three-finger grips of two-dimensional parts performed in a real environment, taking into account both theoretical aspects and unavoidable uncertainties of a grasping action. They build on the existing literature and on physical and mechanical considerations. The measures constitute a feature space that pattern recognition methods can use in order to classify robotic grips according to their quality. Six of the measures depend on the actual finger configuration of the gripper, and they have shown to be critical for better characterization. The kinematics of the Barrett Hand have been used. As a validation step, the measures are merged in two global quality values (with different practical applicability) that can be used to rank feasible candidate grips.

Digital zoom camera with image sharpening and noise suppression

The intention of zooming in a video camera is to obtain more detailed visual information than the full frame view. The optical zooming mechanisms provide this additional information, however, when optically zoomed, the camera no longer detects the full frame view, which was detected before zooming. Digital zooming can detect the full view at all times, however, fails to provide additional visual information when zoomed. In applications such as visual surveillance and manufacturing quality measurement, it is required to detect the full frame view at all times, the camera should be capable of providing additional visual information when zoomed to the region of interest (ROI). This paper presents a video camera system incorporating an autonomous pan, tilt and zoom functionality based on ROI decided upon motion detection capability, which provides more visual information in zoomed modes while detecting the full view at all times. The intelligent ROI decision can be made not only based on motion but also shape, color, sizes etc. of targeted objects for tracking. Image sharpening and noise reduction methods are also provided within the camera system. Standard testing results indicate that this camera system can resolve up to 800 TV lines and produces comparable color quality to other CCD based CCTV surveillance cameras, especially at good lighting conditions.

Retinex processing for automatic image enhancement

The <i>Journal of Electronic Imaging</i> (JEI), copublished bimonthly with the Society for Imaging Science and Technology, publishes peer-reviewed papers that cover research and applications in all areas of electronic imaging science and technology.

Foveation scalable video coding with automatic fixation selection

Image and video coding is an optimization problem. A successful image and video coding algorithm delivers a good tradeoff between visual quality and other coding performance measures, such as compression, complexity, scalability, robustness, and security. In this paper, we follow two recent trends in image and video coding research. One is to incorporate human visual system (HVS) models to improve the current state-of-the-art of image and video coding algorithms by better exploiting the properties of the intended receiver. The other is to design rate scalable image and video codecs, which allow the extraction of coded visual information at continuously varying bit rates from a single compressed bitstream. Specifically, we propose a foveation scalable video coding (FSVC) algorithm which supplies good quality-compression performance as well as effective rate scalability. The key idea is to organize the encoded bitstream to provide the best decoded video at an arbitrary bit rate in terms of foveated visual quality measurement. A foveation-based HVS model plays an important role in the algorithm. The algorithm is adaptable to different applications, such as knowledge-based video coding and video communications over time-varying, multiuser and interactive networks.

Halftone image data hiding with intensity selection and connection selection

In this paper, we propose two novel algorithms, namely intensity selection (IS) and connection selection (CS), that can be applied to the existing halftone image data hiding algorithms DHSPT, DHPT and DHST to achieve improved visual quality. The proposed algorithms generalize the hidden data representation and select the best location out of a set of candidate locations for the application of DHSPT, DHPT or DHST. The two algorithms provide trade-off between visual quality and computational complexity. The IS yields higher visual quality but requires either the original multi-tone image or the inverse-halftoned image which implies high computation requirement. The CS has lower visual quality than IS but requires neither the original nor the inverse-halftoned images. Some objective visual quality measures are defined. Our experiments suggest that significant improvement in visual quality can be achieved, especially when the number of candidate locations is large.

Image quality assessment based on a degradation model

We model a degraded image as an original image that has been subject to linear frequency distortion and additive noise injection. Since the psychovisual effects of frequency distortion and noise injection are independent, we decouple these two sources of degradation and measure their effect on the human visual system. We develop a distortion measure (DM) of the effect of frequency distortion, and a noise quality measure (NQM) of the effect of additive noise. The NQM, which is based on Peli's (1990) contrast pyramid, takes into account the following: 1) variation in contrast sensitivity with distance, image dimensions, and spatial frequency; 2) variation in the local luminance mean; 3) contrast interaction between spatial frequencies; 4) contrast masking effects. For additive noise, we demonstrate that the nonlinear NQM is a better measure of visual quality than peak signal-to noise ratio (PSNR) and linear quality measures. We compute the DM in three steps. First, we find the frequency distortion in the degraded image. Second, we compute the deviation of this frequency distortion from an allpass response of unity gain (no distortion). Finally, we weight the deviation by a model of the frequency response of the human visual system and integrate over the visible frequencies. We demonstrate how to decouple distortion and additive noise degradation in a practical image restoration system.

360 Quality Deterioration of Fresh-cut Onions

A study on quality changes of fresh-cut onions under different temperatures and handling conditions was conducted. High-quality onions were peeled and diced into 1 x 1 cm pieces. Replicated (3) experimental units (150 g) were stored for 20 days in glass jars in a humidified air flow under the following conditions: 0, 5, and 10 °C. To simulate rough handling, onion pieces were rolled with a rolling pin with enough pressure to induce some damage and stored at 5 °C. Objective (color, soluble solids, and dry and fresh weights) and subjective (visual quality, decay, aroma, and discoloration) measurements were taken every 5 days. Fresh and dry weights as well as soluble solid content decrease with storage time and temperature, but decay and development of off-odors increased. An overall browning was observed at the higher temperatures. Colorimeter readings indicate that b* and chroma increased with storage and temperature, while a* values decreased. No definite trends were observed in L* values, and no major differences were found in the hue, although hue tend to be higher with lower temperatures. Rough handling resulted in a faster quality deterioration rate in comparison with pieces stored at the same temperature. At 0 °C, diced onions could be stored satisfactorily for 20 days, although some quality changes took place. At 5 °C visual quality may be acceptable after 10 days of storage, but discoloration started to show up after 5 days, reducing acceptability. Storage at 10 °C only is possible for very short periods of time. Rough handling increases the rate of quality deterioration.

Standardizing visual display quality

The current ISO 9241–3 standard for visual display quality and the proposed user performance tests are reviewed. The standard is found to be more engineering than ergonomic and problems with system configuration, software applications, display settings, user behaviour, wear and physical environment are addressed. Different methods of visual display quality measurement are compared, direct subjective methods are considered to be the most valid and sensitive. Results with the Display Evaluation Scale, a tool for rating visual display quality, are evaluated. Three user groups of the standard are distinguished and a new configuration and content of standards is proposed to suit these user groups.

Analysis of Visual Quality Attributes of White Shrimp by Machine Vision

ABSTRACTAn important component of shrimp quality evaluation is determination of visual attributes by trained inspectors. This is subjective, time consuming, and difficult to quantify. An automated device was developed for repeatable, objective measurement of visual quality of shrimp. The device measured the count, uniformity ratio, color, melanosis, and detected foreign objects. Shrimp area viewed by a camera was used to estimate weight after calibration, and count and uniformity ratio was calculated. The system quantified color changes in white shrimp during iced storage. Melanosis was quantified and correlated with the grading of a trained inspector. The method objectively measured visual quality attributes of white shrimp in less than 1 min per sample.

Robustness of visual image quality measures against various monochromatic aberrations

We examine the correlation between subjective performance and objective image quality metrics, and show that an appropriately defined partial integral of the instrumental modulation transfer function (MTF), called MTFa, gives the best correlation with available psycho-physical data, including those obtained by other investigators. The Strehl ratio and the radius that encircles 84% of the point-spread-function energy also show some correlation with subjective performance, but have considerable limitations. These results begin to make real the possibility that the image quality of visual instruments may be characterized by a single figure of merit within the isoplanatic patch, for all types of monochromatic aberrations.

Acuities through Annular and Central Pupils After Radial Keratotomy

The corneal radius of curvature after radial keratotomy (RK) increases centrally in the surgery-free area while remaining relatively unchanged paracentrally and peripherally in the surgical areas. These corneal topography changes suggest that the imaging properties of the cornea should vary with the area of the cornea allowed to participate in image formation. To test this hypothesis visual acuities were measured both through a central and an annular pupil for normals and RK patients as a function of time after surgery. Annular acuities were decreased significantly after RK and remained decreased over time. Best corrected central acuity increased as a function of time after surgery, becoming significantly better than presurgery acuities but not as good as normals with similar low refractive corrections. Clinical implications include: (1) variations in visual performance (e.g., acuity, contrast sensitivity, glare) and optical quality measures (e.g., refraction, higher-order aberrations) as a function of pupil size; (2) use of a large a surgery-free area as possible; (3) careful centering of the surgery-free area on the natural pupil; (4) new contact lens designs for correcting RK patients' residual refractive error; and (5) counseling patients in general, and patients with naturally large pupils in particular, concerning possible variation in visual function with pupil size. In summary, this study indicates that postsurgery RK paracentral/peripheral corneal optics experience a loss in optical quality as compared to either normal eyes with a low refractive correction or the same eye before surgery.

Measurement of Visual Quality of Paint Coatings for Automobile

Measurement of Visual Quality of Paint Coatings for Automobile

Quality of Alfalfa Hay Chemically Treated at Cutting to Hasten Field Drying

Spray treatment of cut alfalfa with solutions containing emulsified methyl esters of long chain fatty acids and potassium carbonate increased dry matter content above untreated control forage baled at the same time and reduced length of field exposure before baling at a dry matter content “safe” for storage. Bale temperatures, dry matter loss, and changes of visual and analytical quality measurements were greater for control hay baled simultaneously with sprayed alfalfa when respective dry matter contents were 66 and 88%. When both sprayed and unsprayed alfalfas were baled at the same dry matter percent but at different times, analytical measures for resulting hays, bale temperatures, dry matter loss, and changes in analytical measures during storage were similar.

Visual air quality assessment: Denver case study

Studies of visual air quality in the Denver metropolitan region during summer 1979 and winter 1979–1980 are described and results reported. The major objective of the studies was to investigate relationships among four types of variables important to urban visual air quality: (1) individuals' judgements of overall visual air quality; (2) perceptual cues used in making judgments of visual air quality; (3) measurable physical characteristics of the visual environment and (4) concentrations of visibility-reducing pollutants and their precursors. During August 1979 and mid-December 1979 to January 1980, simultaneous measurements of observational and environmental data were made daily at various locations throughout the metropolitan area. Observational data included ratings of overall air quality and related perceptual cues (e.g., distance, clarity, color, border) by multiple observers. Environmental data included routine hourly pollutant and meteorological measurements from several fixed locations within the city, as well as aerosol light scattering and absorption measures from one location. Statistical analyses indicated that (1) multiple perceptual cues are required to explain variation in judgments of overall visual air quality and (2) routine measurements of the physical environment appear to be inadequate predictors of either judgments of overall visual air quality or related perceptual cues.

Visual land use compatibility as a significant contributor to visual resource quality

In this paper an alternative to landscape complexity as a measure of visual landscape quality is presented. This alternative is called visual land use compatibility and is defined as the relationship between adjacent land uses. The research described is part of an interdisciplinary project at the University of Massachusetts called the Metropolitan Landscape Planning Model (METLAND). The Paper discusses man's concern for the relationships between land uses, tracing that concern through history to the present. A procedure that was designed to measure perceptions of the visual aspects of these land use relationships is described. The paper concludes that it appears to be valid to extend the concept of “misfits” into a more general model of both desirable and undesirable aspects of land use relationships and calls for further research to develop that model.