Testing HDR image rendering algorithms

Eight high-dynamic-range image rendering algorithms were tested using ten high-dynamic-range pictorial images. A large-scale paired comparison psychophysical experiment was developed containing two sections, comparing the overall rendering performances and grayscale tone mapping performance respectively. An interval scale of preference was created to evaluate the rendering results. The results showed the consistency of tone-mapping performance with the overall rendering results, and illustrated that Durand and Dorsey’s bilateral fast filtering technique and Reinhard’s photographic tone reproduction have the best rendering performance overall. The goal of this experiment was to establish a sound testing and evaluation methodology based on psychophysical experiment results for future research on accuracy of rendering algorithms

High-Dynamic-Range Photography: Image Display and Perception

Current desktop and hard copy display media are capable of only a limited dynamic range in luminance. Hence, high dynamic range (HDR) images require tone-mapping operators for rendering on these media to adequately reproduce their perceptual qualities. Furthermore, the development of these operators requires a methodology for their evaluation in terms of perceptual attributes. To this end, a series of psychophysical experiments was conducted to evaluate a wide-variety of previously published, HDR tone-mapping operators. The evaluations were conducted in terms of rendering accuracy and image preference, and from them, a general methodology for evaluating tonemapping operators was proposed. A next generation, image appearance model designated as iCAM06 was developed for HDR image rendering and evaluated according to this methodology. The model, based on iCAM02, incorporates the addition of spatial processing properties in the human vision system that include local adaptation for contrast enhancement, rod and cone functions that enhance detail in highlights and shadows, and functions that predict a number of color appearance phenomena. Evaluation of the model proved iCAM06 to have consistently good HDR rendering performance both in preference and accuracy making iCAM06 a good candidate for a general-purpose, tone-mapping operator with potential application to a wide-range of image appearance research and practice

Author's personal copy iCAM06: A refined image appearance model for HDR image rendering Abstract

A new image appearance model, designated iCAM06, was developed for High-Dynamic-Range (HDR) image rendering. The model, based on the iCAM framework, incorporates the spatial processing models in the human visual system for contrast enhancement, photoreceptor light adaptation functions that enhance local details in highlights and shadows, and functions that predict a wide range of color appearance phenomena. Evaluation of the model proved iCAM06 to have consistently good HDR rendering performance in both preference and accuracy making iCAM06 a good candidate for a general-purpose tone-mapping operator with further potential applications to a wide-range of image appearance research and practice

Hadamard Single-Pixel Imaging Based on Positive Patterns

Hadamard single-pixel imaging (SPI) employs the differential measurement strategy to eliminate the effect of negative value of Hadamard basis patterns but leads to doubling the number of measurements. To reduce the number of measurements, a Hadamard SPI method based on positive patterns is proposed. In this method, only the positive patterns are used to acquire measurement values and reconstruct images, so the number of measurements will be reduced by 1/2. Combined with the intensity correlation theory of ghost imaging, the average value of the acquired measures is found; this average value is subtracted from all the measurement values to obtain the spectral coefficients, thus the background noise is eliminated to ensure the imaging quality. Simulation and experimental results show that the proposed method has good noise robustness and can efficiently reconstruct high quality images

Image appearance modeling and high-dynamic-range image rendering

Figure 1: An example of an HDR digital image of the RIT color cube rendered using the iCAM image appearance model to simulate human perception of the scene and (inset) rendered linearly. Recently, the field of color appearance modeling has been extended further into the spatial and temporal domains through efforts known as image appearance modeling. Image appearance models have applications in rendering and visualization of image data, cross-media image and video reproduction, and image quality specification. This paper provides an overview of one such model, iCAM, illustrates several examples of its application, and reviews a psychophysical experiment aimed at evaluating iCAM, and other algorithms for tone mapping of high-dynamicrange (HDR) images

The Effect of Moxibustion Stimulation on Local and Distal Skin Temperature in Healthy Subjects

The aim of this study is to investigate the response of local and distal skin temperature to moxibustion stimulation (MS) and explore the effects of MS on sympathetic nerve activity. The distal skin temperatures of fingertips, as an indicator for sympathetic reflex response, were recorded using infrared camera during resting period (10 min), MS period (10 min), and natural cooling period (15 min), respectively. The MS without ash cleaning (AC) was applied to acupoints Quze (PC3) (Group I) and Lao Gong (PC8) (Group II), respectively. In Group III, the MS with the operation of AC was performed on PC8. The temperature responses of the local stimulation points and corresponding control points were also investigated. At the beginning of MS period, a significant increase of temperature on the stimulation point accompanied by a simultaneous reduction of temperature on fingertips was observed. A marked negative correlation was also obtained between temperature changes in the stimulation point and in the fingertips. At the end of natural cooling period (t = 34 min), the temperature of stimulation point was obviously higher than baseline values. In contrast, the temperatures of fingertips increased and then returned to the baseline levels during the second minute of MS period. In Group III, the temperature of stimulation point increased every time with the operation of AC, accompanied by the temperature decrease of middle fingertip. The findings suggest that moxibustion may trigger the sympathetic nervous system and induce the reduction of microcirculation, accompanied by a reduction of fingertip temperature. In addition, the operation of AC caused repeated cycles of thermal stimulation on the stimulation point, which may repetitively activate cutaneous sympathetic nerve fibres and evoke the temperature reduction of fingertips

High-quality reconstruction of single-pixel imaging using discrete W transform

Single-pixel imaging (SPI) achieves numerous advantages over traditional imaging methods, such as multi-wavelength detection and non-local imaging. In this paper, we report a novel single-pixel imaging technique based on discrete W transform (DWT). In this method, we adopt the star sampling strategy to generate two sets of W basis patterns, these patterns are used to differentially modulate the light source, then the spectrum of the target object is acquired from the light intensities measured by a single-pixel detector. Finally, inverse DWT is utilized the to reconstruct the image. Therefore, high-quality images can be retrieved quickly from sub-Nyquist measurements compared with other transform domain SPI methods. Simulation and experimental results validate the effectiveness of the proposed technique

Evaluating HDR rendering algorithms

A series of three experiments has been performed to test both the preference and accuracy of HDR rendering algorithms in digital photography application. The goal was to develop a methodology for testing a wide-variety of previously published tone-mapping algorithms for overall preference and rendering accuracy. A number of algorithms were chosen and evaluated first in a paired-comparison experiment for overall image preference. A rating-scale experiment was then designed for further investigation of individual image-attributes that make up overall image preference. This was designed to identify the correlations between image attributes and the overall preference results obtained from the first experiments. In a third experiment, three real-world scenes with a diversity of dynamic range and spatial configuration were designed and captured to evaluate seven HDR rendering algorithms for both of their preference and accuracy performance by comparing the appearance of the physical scenes and the corresponding tonemapped images directly. In this series of experiments, a modified Durand & Dorsey’s bilateral filter technique consistently performed well for both preference and accuracy, suggesting that it a good candidate for a common algorithm that could be included in future HDR algorithm testing evaluations. The results of these experiments provide insight for understanding of perceptual HDR image rendering and should aid in design strategies for spatial processing and tone mapping. The results indicate ways to improve and desig