Showing papers on "Tone mapping published in 2005"

High Dynamic Range Imaging: Acquisition, Display, and Image-Based Lighting (The Morgan Kaufmann Series in Computer Graphics)

Abstract: This landmark book is the first to describe HDRI technology in its entirety and covers a wide-range of topics, from capture devices to tone reproduction and image-based lighting. The techniques described enable you to produce images that have a dynamic range much closer to that found in the real world, leading to an unparalleled visual experience. As both an introduction to the field and an authoritative technical reference, it is essential to anyone working with images, whether in computer graphics, film, video, photography, or lighting design. New material includes chapters on High Dynamic Range Video Encoding, High Dynamic Range Image Encoding, and High Dynammic Range Display Devices Written by the inventors and initial implementors of High Dynamic Range Imaging Covers the basic concepts (including just enough about human vision to explain why HDR images are necessary), image capture, image encoding, file formats, display techniques, tone mapping for lower dynamic range display, and the use of HDR images and calculations in 3D rendering Range and depth of coverage is good for the knowledgeable researcher as well as those who are just starting to learn about High Dynamic Range imaging Table of Contents Introduction; Light and Color; HDR Image Encodings; HDR Video Encodings; HDR Image and Video Capture; Display Devices; The Human Visual System and HDR Tone Mapping; Spatial Tone Reproduction; Frequency Domain and Gradient Domain Tone Reproduction; Inverse Tone Reproduction; Visible Difference Predictors; Image-Based Lighting.

Dynamic range reduction inspired by photoreceptor physiology

Abstract: A common task in computer graphics is the mapping of digital high dynamic range images to low dynamic range display devices such as monitors and printers. This task is similar to the adaptation processes which occur in the human visual system. Physiological evidence suggests that adaptation already occurs in the photoreceptors, leading to a straightforward model that can be easily adapted for tone reproduction. The result is a fast and practical algorithm for general use with intuitive user parameters that control intensity, contrast, and level of chromatic adaptation, respectively.

Evaluation of tone mapping operators using a High Dynamic Range display

Abstract: Tone mapping operators are designed to reproduce visibility and the overall impression of brightness, contrast and color of the real world onto limited dynamic range displays and printers. Although many tone mapping operators have been published in recent years, no thorough psychophysical experiments have yet been undertaken to compare such operators against the real scenes they are purporting to depict. In this paper, we present the results of a series of psychophysical experiments to validate six frequently used tone mapping operators against linearly mapped High Dynamic Range (HDR) scenes displayed on a novel HDR device. Individual operators address the tone mapping issue using a variety of approaches and the goals of these techniques are often quite different from one another. Therefore, the purpose of this investigation was not simply to determine which is the "best" algorithm, but more generally to propose an experimental methodology to validate such operators and to determine the participants' impressions of the images produced compared to what is visible on a high contrast ratio display.

Video enhancement using per-pixel virtual exposures

Abstract: We enhance underexposed, low dynamic range videos by adaptively and independently varying the exposure at each photoreceptor in a post-process. This virtual exposure is a dynamic function of both the spatial neighborhood and temporal history at each pixel. Temporal integration enables us to expand the image's dynamic range while simultaneously reducing noise. Our non-linear exposure variation and denoising filters smoothly transition from temporal to spatial for moving scene elements. Our virtual exposure framework also supports temporally coherent per frame tone mapping. Our system outputs restored video sequences with significantly reduced noise, increased exposure time of dark pixels, intact motion, and improved details.

A perceptual framework for contrast processing of high dynamic range images

Abstract: In this work we propose a framework for image processing in a visual response space, in which contrast values directly correlate with their visibility in an image. Our framework involves a transformation of an image from luminance space to a pyramid of low-pass contrast images and then to the visual response space. After modifying response values, the transformation can be reversed to produce the resulting image. To predict the visibility of suprathreshold contrast, we derive a transducer function for the full range of contrast levels that can be found in High Dynamic Range images. We show that a complex contrast compression operation, which preserves textures of small contrast, is reduced to a linear scaling in the proposed visual response space.

Global contrast factor - a new approach to image contrast

Abstract: Contrast in image processing is usually defined as a ratio between the darkest and the brightest spots of an image. In this paper we introduce a different contrast definition. The newly introduced Global Contrast Factor (GCF) corresponds closer to the human perception of contrast. GCF uses contrasts at various resolution levels in order to compute overall contrast. Experiments were conducted in order to find weight factors needed to calculate GCF. GCF measures richness of detail as perceived by a human observer, and as such can be used in various application areas like rendering, tone mapping, volume visualization, and lighting design.

Perceptual evaluation of tone mapping operators with real-world scenes

Abstract: A number of successful tone mapping operators for contrast compression have been proposed due to the need to visualize high dynamic range (HDR) images on low dynamic range devices. They were inspired by fields as diverse as image processing, photographic practice, and modeling of the human visual systems (HVS). The variety of approaches calls for a systematic perceptual evaluation of their performance. We conduct a psychophysical experiment based on a direct comparison between the appearance of real-world scenes and HDR images of these scenes displayed on a low dynamic range monitor. In our experiment, HDR images are tone mapped by seven existing tone mapping operators. The primary interest of this psychophysical experiment is to assess the differences in how tone mapped images are perceived by human observers and to find out which attributes of image appearance account for these differences when tone mapped images are compared directly with their corresponding real-world scenes rather than with each other. The human subjects rate image naturalness, overall contrast, overall brightness, and detail reproduction in dark and bright image regions with respect to the corresponding real-world scene. The results indicate substantial differences in perception of images produced by individual tone mapping operators. We observe a clear distinction between global and local operators in favor of the latter, and we classify the tone mapping operators according to naturalness and appearance attributes.

Perceptually based tone mapping of high dynamic range image streams

Abstract: This paper presents a new perceptually based tone mapping operator that represents scene visibility under timevarying, high dynamic range conditions. The operator is based on a new generalized threshold model that extends the conventional threshold-versus-intensity (TVI) function to account for the viewer's adaptation state, and a new temporal adaptation model that includes fast and slow neural mechanisms as well as photopigment bleaching. These new visual models allow the operator to produce tone-mapped image streams that represent the loss of visibility experienced under changing illumination conditions and in high dynamic range scenes. By varying the psychophysical data that the models use, we simulate the differences in scene visibility experienced by normal and visually impaired observers.

High dynamic range images from low dynamic range images

Abstract: A method for displaying an image includes receiving an image having a first luminance dynamic range and modifying the image to a second luminance dynamic range free from being based upon other images, where the second dynamic range is greater than the first dynamic range. The modified image is displayed on a display.

Perceptual effects in real-time tone mapping

Abstract: Tremendous progress in the development and accessibility of high dynamic range (HDR) technology that has happened just recently results in fast proliferation of HDR synthetic image sequences and captured HDR video. When properly processed, such HDR data can lead to very convincing and realistic results even when presented on traditional low dynamic range (LDR) display devices. This requires real-time local contrast compression (tone mapping) with simultaneous modeling of important in HDR image perception effects such as visual acuity, glare, day and night vision. We propose a unified model to include all those effects into a common computational framework, which enables an efficient implementation on currently available graphics hardware. We develop a post processing module which can be added as the final stage of any real-time rendering system, game engine, or digital video player, which enhances the realism and believability of displayed image streams.

Perceptual image quality: Effects of tone characteristics

Abstract: Tone mapping refers to the conversion of luminance values recorded by a digital camera or other acquisition device, to the luminance levels available from an output device, such as a monitor or a printer. Tone mapping can improve the appearance of rendered images. Although there are a variety of algorithms available, there is little information about the image tone characteristics that produce pleasing images. We devised an experiment where preferences for images with different tone characteristics were measured. The results indicate that there is a systematic relation between image tone characteristics and perceptual image quality for images containing faces. For these images, a mean face luminance level of 46-49 CIELAB L* units and a luminance standard deviation (taken over the whole image) of 18 CIELAB L* units produced the best renderings. This information is relevant for the design of tone-mapping algorithms, particularly as many images taken by digital camera users include faces.

A multigrid solver for boundary value problems using programmable graphics hardware

Abstract: We present a case study in the application of graphics hardware to general-purpose numeric computing. Specifically, we describe a system, built on programmable graphics hardware, able to solve a variety of partial differential equations with complex boundary conditions. Many areas of graphics, simulation, and computational science require efficient techniques for solving such equations. Our system implements the multigrid method, a fast and popular approach to solving large boundary value problems. We demonstrate the viability of this technique by using it to accelerate three applications: simulation of heat transfer, modeling of fluid mechanics, and tone mapping of high dynamic range images. We analyze the performance of our solver and discuss several issues, including techniques for improving the computational efficiency of iterative grid-based computations for the GPU.

Tone mapping of high dynamic range images

Abstract: Tone mapping a high dynamic range (HDR) image is performed by obtaining a log-norm luminance component based on a normalized logarithm of the HDR image. The log-norm luminance component is flattened (tone-compressed) using incrementally-spaced adaptation levels, which are increasingly blurrier representations of the log-norm luminance component, weighted by a diminishing factor. Visual cues are restored by injecting a proportion of values of the log-norm luminance component, applying histogram tail clipping, and applying a sigmoid curve mapping, to create a restored luminance component. A tone-compressed image is obtained by mapping luminance of the HDR image using the restored luminance component and adjusting saturation of the mapped HDR image.

DTM: dynamic tone mapping for backlight scaling

Abstract: This paper proposes an approach for pixel transformation of the displayed image to increase the potential energy saving of the backlight scaling method. The proposed approach takes advantage of human visual system characteristics and tries to minimize distortion between the perceived brightness values of the individual pixels in the original image and those of the backlight-scaled image. This is in contrast to previous backlight scaling approaches which simply match the luminance values of the individual pixels in the original and backlight-scaled images. Moreover, the proposed dynamic backlight scaling approach, which is based on tone mapping, is amenable to highly efficient hardware realization because it does not need information about the histogram of the displayed image. Experimental results show that the dynamic tone mapping for backlight scaling method results in about 35% power saving with an effective distortion rate of 5% and 55% power saving for a 20% distortion rate.

An optimal tone reproduction curve operator for the display of high dynamic range images

Abstract: We present a new tone mapping method for the display of high dynamic range images in low dynamic range devices. We formulate high dynamic range image tone mapping as an optimisation problem. We introduce a two-term cost function, the first term favours linear scaling mapping, the second term favours histogram equalisation mapping, and jointly optimising the two terms optimally maps a high dynamic range image to a low dynamic range image. We control the mapping results by adjusting the relative weightings of the two terms in the objective function. We also present a fast and simple implementation for solving the optimisation problem. We present results to demonstrate that our method works very effectively.

The naturalness of reproduced high dynamic range images

Abstract: The problem of visualizing high dynamic range images on the devices with restricted dynamic range has recently gained a lot of interest in the computer graphics community. Various so-called tone mapping operators have been proposed to face this issue. The field of tone mapping assumes thorough knowledge of both the objective and subjective attributes of an image. However, there no published analysis of such attributes exists so far. In this paper, we present an overview of image attributes which are used extensively in different tone mapping methods. Furthermore, we propose a scheme of relationships between these attributes, leading to the definition of an overall quality measure which we call naturalness. We present results of the subjective psychophysical testing that we have performed to prove the proposed relationship scheme. Our effort sets the stage for well-founded quality comparisons between tone mapping operators. By providing good definitions of the different attributes, comparisons, be they user-driven or fully automatic, are made possible at all.

Perceptual Effects in Real-Time Tone Mapping

Abstract: Tremendous progress in the development and accessibility of high dynamic range (HDR) technology that has happened just recently results in fast proliferation of HDR synthetic image sequences and captured HDR video. When properly processed, such HDR data can lead to very convincing and realistic results even when presented on traditional low dynamic range (LDR) display devices. This requires real-time local contrast compression (tone mapping) with simultaneous modeling of important in HDR image perception effects such as visual acuity, glare, day and night vision. We propose a unified model to include all those effects into a common computational framework, which enables an efficient implementation on currently available graphics hardware. We develop a post processing module which can be added as the final stage of any real-time rendering system, game engine, or digital video player, which enhances the realism and believability of displayed image streams.

High dynamic range volume visualization

Abstract: High resolution volumes require high precision compositing to preserve detailed structures. This is even more desirable for volumes with high dynamic range values. After the high precision intermediate image has been computed, simply rounding up pixel values to regular display scales loses the computed details. In this paper, we present a novel high dynamic range volume visualization method for rendering volume data with both high spatial and intensity resolutions. Our method performs high precision volume rendering followed by dynamic tone mapping to preserve details on regular display devices. By leveraging available high dynamic range image display algorithms, this dynamic tone mapping can be automatically adjusted to enhance selected features for the final display. We also present a novel transfer function design interface with nonlinear magnification of the density range and logarithmic scaling of the color/opacity range to facilitate high dynamic range volume visualization. By leveraging modern commodity graphics hardware and out-of-core acceleration, our system can produce an effective visualization of huge volume data.

Comprehensive Fast Tone Mapping for High Dynamic Range Image Visualization

Abstract: In this paper, we present a comprehensive tone reproduction curve based operator for the fast visualization of high dynamic range images. Image reproduction is a highly subjective process and different users will have very different preferences even for the same image. Therefore, a really useful tone-mapping tool for high dynamic range images should be fast and interactive, with which users can interactively adjust the mapping parameters and instantly visualize the results. Furthermore, there should be as few adjustable parameters as possible, and equally important, the parameters should have a clear, intuitive and straightforward relationship with the appearance of the mapped images to guide the users to adjust the parameters. Based on these requirements, we have developed a comprehensive tone reproduction curve based mapping technology. Our technique has two intuitive variables, which can be adjusted at an interactive speed even for very large images. One parameter controls the overall brightness of the reproduction and the other adjusts the detail and contrast 1 of the result. A piece of easy to use high dynamic range image visualization software that implements our operator is publicly available.

Real-time realistic rendering and high dynamic range image display and compression

Abstract: This dissertation focuses on the many issues that arise from the visual rendering problem. Of primary consideration is light transport simulation, which is known to be computationally expensive. Monte Carlo methods represent a simple and general class of algorithms often used for light transport computation. Unfortunately, the images resulting from Monte Carlo approaches generally suffer from visually unacceptable noise artifacts. The result of any light transport simulation is, by its very nature, an image of high dynamic range (HDR). This leads to the issues of the display of such images on conventional low dynamic range devices and the development of data compression algorithms to store and recover the corresponding large amounts of detail found in HDR images. This dissertation presents our contributions relevant to these issues. Our contributions to high dynamic range image processing include tone mapping and data compression algorithms. This research proposes and shows the efficacy of a novel level set based tone mapping method that preserves visual details in the display of high dynamic range images on low dynamic range display devices. The level set method is used to extract the high frequency information from HDR images. The details are then added to the range compressed low frequency information to reconstruct a visually accurate low dynamic range version of the image. Additional challenges associated with high dynamic range images include the requirements to reduce excessively large amounts of storage and transmission time. To alleviate these problems, this research presents two methods for efficient high dynamic range image data compression. One is based on the classical JPEG compression. It first converts the raw image into RGBE representation, and then sends the color base and common exponent to classical discrete cosine transform based compression and lossless compression, respectively. The other is based on the wavelet transformation. It first transforms the raw image data into the logarithmic domain, then quantizes the logarithmic data into the integer domain, and finally applies the wavelet based JPEG 2000 encoder for entropy compression and bit stream truncation to meet the desired bit rate requirement. We believe that these and similar such contributions will make a wide application of high dynamic range images possible. (Abstract shortened by UMI.)

Hierarchical tone mapping for high dynamic range image visualization

Abstract: In this paper, we present a computationally efficient, practically easy to use tone mapping techniques for the visualization of high dynamic range (HDR) images in low dynamic range (LDR) reproduction devices. The new method, termed hierarchical nonlinear linear (HNL) tone-mapping operator maps the pixels in two hierarchical steps. The first step allocates appropriate numbers of LDR display levels to different HDR intensity intervals according to the pixel densities of the intervals. The second step linearly maps the HDR intensity intervals to theirs allocated LDR display levels. In the developed HNL scheme, the assignment of LDR display levels to HDR intensity intervals is controlled by a very simple and flexible formula with a single adjustable parameter. We also show that our new operators can be used for the effective enhancement of ordinary images.

A Simple Spatial Tone Mapping Operator for High Dynamic Range Images.

Abstract: We present a simple and effective tone mapping operator, that preserves visibility and contrast impression of high dynamic range images. The method is conceptually simple, and easy to use. We use a s-function type operator which takes into account both the global average of the image, as well as local luminance in the immediate neighborhood of each pixel. The local luminance is computed using a median filter. It is seen that the resulting low dynamic range image preserves fine details, and avoids common artifacts such as halos, gradient reversals or loss of local contrast. Introduction The real world scenes often have a very high range of luminance values. While digital imaging technology now enables us to capture full dynamic range of the real world scene, still we are limited by the low dynamic range displays. Thus the scene can be visualized on a display monitor only after the captured high dynamic range is compressed to available range of the display device. This has been referred to as the tone mapping problem in the literature and a great deal of work has been done in this area by using a mapping that varies spatially depending on the neighborhood of a pixel, often at multiple scales [Pattanaik et.al. 1998; Fattal et.al. 2002;Reinhard et. al 2002; Durand and Dorsey 2002]. [Johnson and Fairchild 2003] have shown how accurate color predictions can be made for tone mapping high dynamic range images. The rendering performance of some of these algorithms has been recently reported in [Kuang et. al 2004]. In this paper we propose a simple tone mapping operator which allows us to preserve the visual content of the real-world scene without the user having to manually set a number of parameters. We show that by using a log of relative luminance at a pixel with respect to its local luminance in a small neighborhood, the standard s-function can be modified to yield visually pleasing results. Further it is also proposed that the local luminance be computed using a median filter, which provides a stronger central indicator than the mean filter. The operator The global contrast helps us to differentiate between various regions of the HDR (high dynamic range) image, which we can loosely classify as dark, dim, lighted, bright etc. Within each region objects become distinguishable due to local contrast against the background – either the object is darker than the background or it is brighter than the background. If the HDR image consisted of only regions of uniform illuminations, the following s-function would compress the range of illumination across the image, to displayable luminance YD in the range 0 -1. YD(x, y) = Y(x, y) / [Y(x, y) + GC] (1) where GC is the global contrast factor computed through

The Influence of Luminance on Local Tone Mapping

Abstract: We study the influence of the choice of color space for local tone mapping methods. Many local tone mapping methods do not perform well when applied independently to the three color channels of an RGB image. A common solution is to only treat the luminance channel. However, the question of which color space provides the most suitable luminance definition has not been addressed. The correlation between luminance and chrominance is known to have an influence on the rendered image but the relation between a measure of correlation and the appearance of the image has not yet been found. We consider four color transforms and introduce a measure to evaluate how well they decorrelate luminance and chrominance information. We apply two local tone mapping algorithms to the luminance channel given by the four transforms and visually compare the results. As each transform leads to another luminance definition, the resulting color images will be different as well. Our results confirm that less correlation between luminance and chrominance results in better performance of the local tone mapping algorithms. Namely, they provide a better increase in local contrast in the luminance channel and less hue shifts. However, we show that a perfect decorrelation is not always necessary.

Spectral information and spatial color computation

Abstract: In real world no color exists. Only spectral light distributions interact to form the final color sensation. This paper presents preliminary experiments whose purpose is to test the robustness of a spatial color computation in relation to changes in the acquisition of spectral information. The basic idea is that human vision system has evolved into a robust system to acquire visual information, in this case the color, adapting to varying illumination conditions to guarantee color constancy. The presented experiments test changes in the output of a Retinex-derived tone mapping operator, varying illuminants and color matching function curves. Synthetic high dynamic range multispectral images have been computed by a photometric ray tracer using different illuminants. Then, using standard and modified color matching functions, a set of high dynamic range RGB images has been created. This set has been converted to standard RGB images using a linear tone mapping algorithm with no spatial color computation and one based on Retinex, performing a spatial color normalization. A discussion of the results is presented.

Learning Mandarin tone mapping codebook for voice conversion

Abstract: The phonetics properties of Chinese Mandarin features clearly demarcated syllables with tonal phonemes. A tone codebook mapping method is proposed to obtain a better performance in voice conversion of Chinese Mandarin speech than the conventional conversion method, which focuses mainly on the short-time spectral envelopes. The pitch contour of the whole Mandarin syllable is used as a unit type for pitch conversion. The syllable pitch contours are first extracted from the source and target utterances. Time normalization and moving average filtering are then performed on them. These preprocessed pitch contours are classified to generate the source and target tone code-books, and by associating them a Mandarin tone mapping codebook is finally obtained in terms of speech alignment. Experimental results show that the proposed tone codebook mapping method in voice conversion can give a good performance in Chinese Mandarin speech.

Dual Prominence of Tone Mapping: A Case of Tone Movement

Abstract: The present paper proposes a theory of dual prominence in tone mapping. Evidence is drawn from tone movement observed in the lexical tone sandhi of the Chinese Zhenhai dialect. In this theory, two prominent positions, prosodic edge and metrical head, are singled out in phonology. They are referred to by both positional faithfulness and positional markedness constraints in an Optimality-Theoretic analysis of tone movement. Most tone sandhi processes in Chinese Wu dialects are characterized as deletion of tones on unstressed syllables, followed by spreading (or re-association) of the tone on the stressed syllable in a tone sandhi domain. An often-cited example is New Shanghai, which has five lexical tones, three long tones and two short checked tones (marked by ). Its tone inventory is given in (1):

Designing a tone mapping algorithm for road visibility experiments

Abstract: Road visibility studies can take strong benefit from the use of computer graphics images through driving simulation and psychovisual experiments. But display devices are unable to render the complex visual environment of the driver. A Tone Mapping (TM) algorithm aims to convert high dynamic radiance (HDR) images into images that can be displayed. The goal of our TM algorithm is to preserve the visual perception of the observer.

Sketch based facial expression recognition using graphics hardware

Abstract: In this paper, a novel system is proposed to recognize facial expression based on face sketch, which is produced by programmable graphics hardware-GPU(Graphics Processing Unit). Firstly, an expression subspace is set up from a corpus of images consisting of seven basic expressions. Secondly, by applying a GPU based edge detection algorithm, the real-time facial expression sketch extraction is performed. Subsequently, noise elimination is carried out by tone mapping operation on GPU. Then, an ASM instance is trained to track the facial feature points in the sketched face image more efficiently and precisely than that on a grey level image directly. Finally, by the normalized key feature points, Eigen expression vector is deduced to be the input of MSVM(Multi-SVMs) based expression recognition model, which is introduced to perform the expression classification. Test expression images are categorized by MSVM into one of the seven basic expression subspaces. Experiment on a data set containing 500 pictures clearly shows the efficacy of the algorithm.

High Dynamic Range Compression on Programmable Graphics Hardware

Abstract: Present a system for compressing high dynamic range images to fit conventional display devices that are only capable of outputting a low dynamic range.In addition to manipulating the gradient field of luminance image by attenuating the large gradients'magnitudes,it can preserve fine details,resulting in an image which provokes the same responses as someone would have viewing the scene in the real world.Specifically, with the whole process built on programmable graphics hardware,present an efficient algorithm based on GPU acceleration and provide a fast dynamic range compression technique.Furthermore, describe a framework for rendering high dynamic range images in real time.It not only can be used in image based tone mapping but also is able to be a core technique in interactive graphics applications.