13:45
JIST-first: Matrix R-based Visual Response to Optimal Colors and Application to Image Color Gamut Expansion, Hiroaki Kotera, Kotera Imaging Laboratory (Japan)
[view abstract]
The optimal colors with maximum chroma at constant lightness present an ideal target for the colorants pursuing the ultimate wide color gamut. MacAdam proved that optimal colors are composed of square pulse-shaped spectra with at least two tansition wavelengths λ1 and λ2 whose reflectances change from 0 to 1 or 1 to 0. The optimal color gamut is created from two-types, a convex-type with reflectance 1.0 in w = λ1 ~ λ2 and 0.0 otherwise, or a concave-type with reflectance 0.0 in w = λ1 ~ λ2 and 1.0 otherwise. It takes a high computation cost to search the optimal color candidates in high precision and to create the 3D color gamut. In addition, the human visual spectral responses to the optimal color spectra remain unknown. This paper (1) proposes an alternative simple method for creating the optimal color gamut with GBD (Gamujt Boundary Descriptor) technique, and (2) clarifies how human vision spectrally respond to the optimal colors based on Matrix-R theory, for the first time which was unknown until now, and (3) presents centroid-invariant novel color gamut expansion method considering the optimal color as an ideal target and finally apply it to actual low-saturation images to verify its effect.
14:05
Effect of Display Characteristics and Color Reproduction Method in Computerized Color Vision Test, Dan Zhang, Shining Ma, Yue Liu, Yongtian Wang, and Weitao Song, Beijing Institute of Technology (China)
[view abstract]
A simulation was performed using simulated displays to examine how the results of the computerized color vision test are influenced by display characteristics, and color reproduction methods. In this work, the color difference between the background and the number in the test plates was employed to quantify the visibility of the target number in the computerized test. The results have indicated that for the color-appearance-based reproduction method, the impact of display characteristics on the target visibility is minimal except for the displays with extremely narrow bandwidth. While for the tristimulus-based reproduction method, it is necessary to consider display characteristics for the computerized color vision test.
14:25
Analyzing Perceptual Uniformity using Jacobian Determinants, David A. LeHoty, Independent Researcher (US), and Charles Poynton, Independent Researcher (Canada)
[view abstract]
The CIE LAB color space was established by color scientists to be approximately perceptually uniform. The Y′CBCR color space is widely assumed by video engineers to be approximately perceptually uniform. However, these two color spaces have quite different transforms from tristimuli (radiometric) coordinates; they clearly cannot have the same perceptual performance.
It is instructive to ask: Where in color space is Y′CBCR quantization the worst, when evaluated in terms of LAB? And, conversely, where in color space does LAB quantize most coarsely, when evaluated in Euclidean Y′CBCR difference?
The Jacobian corresponding to a color coordinate in 3 space is a 3 × 3 matrix of partial derivatives. The determinant of that matrix is analogous to volume. We compute numerical Jacobian determinants to explore how unit LAB volumes at sample points spanning a target color space map to volumes in Y′CBCR. Where that volume is quite large, we expect poor perceptual performance of Y′CBCR. Where that volume is quite small, Y′CBCR is over-quantizing, and may have poor codeword utilization – but in such regions it’s reasonable to suspect the performance of LAB.
We present “heat maps” that visualize where Y′CBCR performs poorly compared to LAB (and vice versa).
14:45
The Influence of Interreflections on Shape from Fluorescence, Irina-Mihaela Ciortan, Sony George, and Jon Yngve Hardeberg, Norwegian University of Science and Technology (Norway)
[view abstract]
Fluorescence is an optical phenomenon, specific to certain materials that absorb light with higher energy and re-emit it at lower energy, with unnoticeable time latency. Due to this so-called Stokes shift, fluorescent materials pose several challenges in image capture, where usually a filtering setup is required at the illumination and/or sensing ends. Nevertheless, fluorescence emission is diffuse, which was previously used in shape from photometry models. In this work, we target the shape from fluorescence method for a specific category of materials: those with overlapping reflectance and fluorescence signals. In particular, we investigate how the self-interreflections (light bounces off a surface that get re-reflected by the surface itself) change the appearance of scenes with such fluorescent materials and how this affects the shape estimation with a photometric stereo model. To avoid instrumental artifacts inherent in real image capture setups, we perform our analysis on a synthetic dataset of multi-light images, generated with a physically-based spectral renderer that supports fluorescence.
15:05 - 15:30
Coffee Break
Applications
15:30 - 16:30
Session Chair: Luke Hellwig, Samsung (US)
15:30
The Role of Colour and Texture on Fabric Image Preference, Qinyuan Li, Kaida Xiao, Michael Pointer, and Ningtao Mao, University of Leeds (UK)
[view abstract]
Colour and texture characteristics convey most of the information of an image and influence human perception as contributing factors to perceived preference. How the colour, together with the texture characteristics affects fabric image preference is not fully understood. In the present study, we firstly took texture characteristics from the perspective of image analysis techniques into consideration to evaluate the role of colour and texture in fabric image preference. The results showed that, even though colour characteristics play an important role, the addition of texture features, lead to better predictive performance in the evaluation of fabric image preference using machine learning techniques.
15:50
JIST-first: Characterization of Wood Materials using Perception-related Image Statistics, Jiří Filip and Veronika Vilímovská, The Czech Academy of Sciences, Institute of Information Theory and Automation (Czech Republic)
[view abstract]
An efficient computational characterization of real-world materials is one of the challenges in image understanding. An automatic assessment of materials, with similar performance as human observer, usually relies on complicated image filtering derived from models of human perception. However, these models become too complicated when a real material is observed in the form of dynamic stimuli. This study tackles the challenge from the other side. First, we collected human ratings of the most common visual attributes for videos of wood samples and analyzed their relationship to selected image statistics. In our experiments on a set of sixty wood samples, we have found that such image statistics can perform surprisingly well in the discrimination of individual samples with reasonable correlation to human ratings. We have also shown that these statistics can be also effective in the discrimination of images of the same material taken under different illumination and viewing conditions.
16:10
JIST-first: Color Performance Review (CPR): A Color Performance Analyzer for Endoscopy Devices, Wei-Chung Cheng, U.S. Food and Drug Administration (US)
[view abstract]
Color performance is an important safety and performance attribute of endoscopes. An endoscope that exhibits poor color performance inadequately reproduces color images and may make it difficult for the endoscopist to visualize features needed for diagnostic or therapeutic tasks. Various color performance testing methods have been developed to evaluate color fidelity of endoscopes since 1987. However, these testing methods have limited utility because most endoscopes cannot and do not intend to reproduce the original color faithfully. In this work, endoscope color performance is reviewed by evaluating preservation of color contrast between patches and preservation of the patch order in lightness, hue, and chroma. The analysis method was implemented as the Color Performance Review (CPR) tool and is available in the catalog of Regulatory Science Tools published by FDA/CDRH/OSEL.
16:30
Best Student Paper announced and Closing remark