Perceptibility and acceptability of JPEG 2000 compressed images of various scene types

This investigation examines the relationships between image fidelity, acceptability thresholds and scene content for images distorted by lossy compression. Scene characteristics of a sample set of images, with a wide range of representative scene content, were quantified, using simple measures (scene metrics), which had been previously found to correlate with global scene lightness, global contrast, busyness, and colorfulness. Images were compressed using the lossy JPEG 2000 algorithm to a range of compression ratios, progressively introducing distortion to levels beyond the threshold of detection. Twelve observers took part in a paired comparison experiment to evaluate the perceptibility threshold compression ratio. A further psychophysical experiment was conducted using the same scenes, compressed to higher compression ratios, to identify the level of compression at which the images became visually unacceptable. Perceptibility and acceptability thresholds were significantly correlated for the test image set; both thresholds also correlated with the busyness metric. Images were ranked for the two thresholds and were further grouped, based upon the relationships between perceptibility and acceptability. Scene content and the results from the scene descriptors were examined within the groups to determine the influence of specific common scene characteristics upon both thresholds

Experimental approach to the use of objective metrics for estimating chromatic quality in the digitization of graphical documents

Se abordan de una forma crítica diferentes aproximaciones aplicables para la realización de modelos de sistemas de control de calidad automatizado de imágenes digitales en proyectos de digitalización de fondos fotográficos con valor histórico-cultural. Tras la realización de un experimento psicométrico con cuatro expertos humanos se concluye que no es posible utilizar con un buen rendimiento los modelos simplistas de uso común basados en rangos de aceptación continuos sobre mediciones de color tomadas de forma aislada. Nuestra investigación demuestra que un modelo basado en un sistema de reglas obtenidas por aprendizaje automático que emplee las métricas CIE 1976 o CIEDE 2000, junto con los atributos perceptuales de color matiz, saturación y luminosidad, emula a los expertos humanos en calidad de imagen con un alto grado de eficacia, por encima del 85%.This work aims to provide a critical examination of different approaches to creating models of automated quality control systems for digital images in digitization projects for photographic heritage collections. After conducting a psychometric experiment with four human experts, we demonstrate that it is not possible to talk about commonly used, simplistic models based on continuous acceptance ranges for colour metrics on an isolated basis. This study demonstrates that a model based on a rule-based, machine-learning system employing metrics (CIE 1976 or CIEDE 2000) along with the colour perceptual attributes of hue, saturation and lightness, emulates the image quality experts with a high degree of efficacy, above 85%

Damage function for historic paper. Part I: Fitness for use

Background In heritage science literature and in preventive conservation practice, damage functions are used to model material behaviour and specifically damage (unacceptable change), as a result of the presence of a stressor over time. For such functions to be of use in the context of collection management, it is important to define a range of parameters, such as who the stakeholders are (e.g. the public, curators, researchers), the mode of use (e.g. display, storage, manual handling), the long-term planning horizon (i.e. when in the future it is deemed acceptable for an item to become damaged or unfit for use), and what the threshold of damage is, i.e. extent of physical change assessed as damage. Results In this paper, we explore the threshold of fitness for use for archival and library paper documents used for display or reading in the context of access in reading rooms by the general public. Change is considered in the context of discolouration and mechanical deterioration such as tears and missing pieces: forms of physical deterioration that accumulate with time in libraries and archives. We also explore whether the threshold fitness for use is defined differently for objects perceived to be of different value, and for different modes of use. The data were collected in a series of fitness-for-use workshops carried out with readers/visitors in heritage institutions using principles of Design of Experiments. Conclusions The results show that when no particular value is pre-assigned to an archival or library document, missing pieces influenced readers/visitors’ subjective judgements of fitness-for-use to a greater extent than did discolouration and tears (which had little or no influence). This finding was most apparent in the display context in comparison to the reading room context. The finding also best applied when readers/visitors were not given a value scenario (in comparison to when they were asked to think about the document having personal or historic value). It can be estimated that, in general, items become unfit when text is evidently missing. However, if the visitor/reader is prompted to think of a document in terms of its historic value, then change in a document has little impact on fitness for use

Evaluating the 1931 CIE Color-Matching Functions

The use of colorimetry within industry has grown extensively in the last few decades. Central to many of today\u27s instruments is the CIE system, established in 1931. Many have questioned the validity of the assumptions made by Wright1 and Guild,2 some suggesting that the 1931 color-matching functions are not the best representation of the human visual system\u27s cone responses. A computational analysis was performed using metameric data to evaluate the CIE 1931 color-matching functions as compared to with other responsivity functions. The underlying assumption was that an optimal set of responsivity functions would yield minimal color-difference error between pairs of visually matched metamers. The difference of average color differences found in the six chosen sets of responsivity functions was small. The CIE 1931 2° color-matching functions on average yielded the largest color difference, 4.56 E. The best performance came from the CIE 1964 10° color-matching functions, which yielded an average color difference of 4.02 E. An optimization was then performed to derive a new set of color-matching functions that were visually matched using metameric pairs of spectral data. If all pairs were to be optimized to globally minimize the average color difference, it is expected that this would produce an optimal set of responsivity functions. The optimum solution was to use a weighted combination of each set of responsivity functions. The optimized set, called the Shaw and Fairchild responsivity functions, was able to reduce the average color difference to 3.92 E. In the final part of this study a computer-based simulation of the color differences between the sets of responsivity functions was built. This simulation allowed a user to load a spectral radiance or a spectral reflectance data file and display the tristimulus match predicted by each of the seven sets of responsivity functions

A review of air pollution impact on subjective well-being: Survey versus visual psychophysics

Air pollution is a worldwide environmental and health issue, especially in major developing countries. A recent World Health Organization report shows about 3 million deaths in the world in 2012 are due to ambient air pollution and China and India are the countries with the most severe challenge. Air pollution influences people's thought and experience of their lives directly by visual perceptions. This reduces people's subjective well-being (SWB) to a significant degree. Empirical researchers have made efforts to examine how self-reported well-being varies with air quality typically by survey method - matching SWB data with monitored air pollution data. Their findings show NO2, particles, lead, SO2 and O3 have significant negative impact on SWB. However, it is very hard to match air pollution characteristics from monitor stations with each respondent's state of SWB at the moment a survey is conducted. Also it is very hard to find the detailed trend impact from only air pollution factor on SWB. This review illustrates the features and limitations of previous survey studies on quantifying the effects of air pollution on subjective well-being. This review further displays the progress of psychophysics and its application in landscape and air quality research. We propose using psychophysics application to quantify air pollution impact on SWB