A scheme is developed for classifying the types of motion perceived by a humanlike robot. It is assumed that the robot receives visual images of the scene using a perspective system model. Equations, theorems, concepts, clues, etc., relating the objects, their positions, and their motion to their images on the focal plane are presented. >

http://ieeexplore.ieee.org/iel2/815/3148/00100651.pdf

Robot vision

We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to High dynamic range (HDR) first. Skipping the physically based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators.

Exposure Fusion: A Simple and Practical Alternative to High Dynamic Range Photography

Tone-mapping operators (TMOs) that convert high dynamic range (HDR) to low dynamic range (LDR) images provide practically useful tools for the visualization of HDR images on standard LDR displays. Different TMOs create different tone-mapped images, and a natural question is which one has the best quality. Without an appropriate quality measure, different TMOs cannot be compared, and further improvement is directionless. Subjective rating may be a reliable evaluation method, but it is expensive and time consuming, and more importantly, is difficult to be embedded into optimization frameworks. Here we propose an objective quality assessment algorithm for tone-mapped images by combining: 1) a multiscale signal fidelity measure on the basis of a modified structural similarity index and 2) a naturalness measure on the basis of intensity statistics of natural images. Validations using independent subject-rated image databases show good correlations between subjective ranking score and the proposed tone-mapped image quality index (TMQI). Furthermore, we demonstrate the extended applications of TMQI using two examples - parameter tuning for TMOs and adaptive fusion of multiple tone-mapped images.

/pdf/objective-quality-assessment-of-tone-mapped-images-3q1qnzs1dr.pdf

Objective Quality Assessment of Tone-Mapped Images

We present an image-based modeling and editing system that takes a single photo as input. We represent a scene as a layered collection of depth images, where each pixel encodes both color and depth. Starting from an input image, we employ a suite of user-assisted techniques, based on a painting metaphor, to assign depths and extract layers. We introduce two specific editing operations. The first, a “clone brushing tool,” permits the distortion-free copying of parts of a picture, by using a parameterization optimization technique. The second, a “texture-illuminance decoupling filter,” discounts the effect of illumination on uniformly textured areas, by decoupling large- and small-scale features via bilateral filtering. Our system enables editing from different viewpoints, extracting and grouping of image-based objects, and modifying the shape, color, and illumination of these objects.

/pdf/image-based-modeling-and-photo-editing-2ye7pvltxg.pdf

Image-based modeling and photo editing

Color science is a multidisciplinary field with broad applications in industries such as digital imaging, coatings and textiles, food, lighting, archiving, art, and fashion. Accurate definition and measurement of color appearance is a challenging task that directly affects color reproduction in such applications. Color Appearance Models addresses those challenges and offers insight into the preferred solutions. Extensive research on the human visual system (HVS) and color vision has been performed in the last century, and this book contains a good overview of the most important and relevant literature regarding color appearance models.

https://www.spiedigitallibrary.org/journals/Journal-of-Electronic-Imaging/volume-23/issue-2/029901/Color-Appearance-Models/10.1117/1.JEI.23.2.029901.pdf

Color Appearance Models

We propose a fast, high quality tone mapping technique to display high contrast images on devices with limited dynamic range of luminance values. The method is based on logarithmic compression of luminance values, imitating the human response to light. A bias power function is introduced to adaptively vary logarithmic bases, resulting in good preservation of details and contrast. To improve contrast in dark areas, changes to the gamma correction procedure are proposed. Our adaptive logarithmic mapping technique is capable of producing perceptually tuned images with high dynamic content and works at interactive speed. We demonstrate a successful application of our tone mapping technique with a high dynamic range video player enabling to adjust optimal viewing conditions for any kind of display while taking into account user preference concerning brightness, contrast compression, and detail reproduction.

/pdf/adaptive-logarithmic-mapping-for-displaying-high-contrast-1bph2oxtis.pdf

Adaptive Logarithmic Mapping For Displaying High Contrast Scenes

High dynamic range (HDR) photography and physically based rendering produce images with full range of luminance data. The problem of mapping real world luminance into the limited luminance range of display devices has been addressed in the last decade through the development of many different tone mapping algorithms (see [Devlin et al. 2002] for a recent survey). Clearly, a sound methodology for comparing existing algorithms is needed to understand their strengths and weaknesses; this work takes a first exploratory step towards achieving this goal. We performed a series of psychophysical experiments in which human subjects assessed their perceptions associated with a set of 24 images, constructed by submitting four different scenes (both synthetic and photographic) to six popular tone mapping operators: Photographic Tone Reproduction (Reinhard et al. 2002), Uniform Scaling Quantization (Schlick 1994), Retinex (Frankle et al. 1983), Visual Adjustment (Ferwerda 1996), Revised Tumblin-Rushmeier (1993), and Histogram Adjustment (Ward et al. 1997; the human contrast sensitivity option was switched off). In this initial attempt, we chose an exploratory rather than confirmatory approach in which subjects first made global judgments regarding how perceptually similar or dissimilar the images were, without specifying the ways in which they might differ from one another. Global dissimilarity judgments were made for all pairwise comparisons of the six tone mapping operators separately for each of the four scenes by each of 11 subjects, and these data were submitted to INdividual DifferencesSCALing (INDSCAL) analysis. The primaryINDSCAL result of interest is a derivedStimulus Spacein which each stimulus is assigned coordinates on the dimensions describing the perceptual differences between the stimuli (see [Borg and Groenen 1997] for background on this analysis method). The spatial configuration of the six tone mappers on the two most salient dimensions is shown in Figure 1.

Perceptual evaluation of tone mapping operators

For years, 24-bit images effectively using 256 values for each color channel wereconsidered accurate enough to be used in the creation and display of photorealisticimagery. On the other end, photographers knowing the limitation of cameras andﬁlms would never attempt to photograph a scene including a light source placed inthe camera’s ﬁeld of vision. However, as a result of global illumination renderingand high dynamic range (HDR) imaging [DM97], it is now common to generateimages spanning a huge range of luminance. Dealing with such images in elec-tronic form requires extending ﬁle formats that are restricted to too few luminancevalues and colors. An even more serious issue is effective displaying/printing ofthose images using media with limited dynamic range (both in reproducible lumi-nance values and color gamut).The ﬁrst limitation was successfully addressed in different pixel encoding for-mats. A simple approach relies on using three ﬂoating point numbers for eachpixel RGB values, however, this leads to excessive ﬁle sizes. The HDR imagesize can be reduced to four bytes for each pixel using the RGBE format [War91],in which a common exponent and a mantissa are assumed for each channel thusallowing a wide dynamic range with little storage overhead. Another format, thelogLuv encoding for tiff images [Lar98] separates a logarithmic representation ofluminance and aCIE

http://resources.mpi-inf.mpg.de/hdr/TMO/DragoTechRep.pdf

Perceptual Evaluation of Tone Mapping Operators with Regard to Similarity and Preference

Validation proposal for global illumination and rendering techniques

A tone mapping algorithm for displaying high contrast scenes
was designed on the basis of the results of experimental tests using human subjects. Systematic perceptual evaluation of several existing tone mapping techniques revealed that the most "natural" appearance was determined by the presence in the output image of detailed scenery features often made visible by limiting contrast and by properly reproducing brightness. Taking these results into account, we developed a system to produce images close to the ideal preference point for high dynamic range input image data. Of the algorithms that we tested, only the Retinex algorithm was capable of retrieving detailed scene features hidden in high luminance areas
while still preserving a good contrast level. This paper presents changes made to Retinex algorithm for processing high dynamic range images, and a further integration of the Retinex with specialized tone mapping algorithms that enables the production of images that appear as similar as possible to the viewer's perception of actual scenes.

/pdf/design-of-a-tone-mapping-operator-for-high-dynamic-range-1pntb8et0z.pdf

Frédéric Drago

Papers

Adaptive Logarithmic Mapping For Displaying High Contrast Scenes

Perceptual evaluation of tone mapping operators

Perceptual Evaluation of Tone Mapping Operators with Regard to Similarity and Preference

Validation proposal for global illumination and rendering techniques

Design of a Tone Mapping Operator for High Dynamic Range Images Based upon Psychophysical Evaluation and Preference Mapping