ESTIMATING FACIAL ALBEDO FROM A SINGLE IMAGE

2006 ◽  
Vol 20 (06) ◽  
pp. 955-970 ◽  
Author(s):  
WILLIAM A. P. SMITH ◽  
EDWIN R. HANCOCK
Keyword(s):  
Statistical Model ◽  
Normal Direction ◽  
Reconstructed Image ◽  
Intensity Data ◽  
Single Image ◽  
Image Brightness ◽  
Image Intensity ◽  
Surface Normal

This paper describes how a facial albedo map can be recovered from a single image using a statistical model that captures variations in surface normal direction. We fit the model to intensity data using constraints on the surface normal direction provided by Lambert's law and then use the differences between observed and reconstructed image brightness to estimate the albedo. We show that this process is stable under varying illumination. We then show how eigenfaces trained on albedo maps may provide a better representation for illumination insensitive recognition than those trained on raw image intensity.

scholarly journals Single Image-Based Vignetting Correction for Improving the Consistency of Neural Activity Analysis in 2-Photon Functional Microscopy

2022 ◽  
Vol 15 ◽  
Author(s):  
Dong Li ◽  
Guangyu Wang ◽  
René Werner ◽  
Hong Xie ◽  
Ji-Song Guan ◽  
...  
Keyword(s):  
Neural Activity ◽  
Present Report ◽  
Activity Patterns ◽  
Quantitative Measure ◽  
Image Data ◽  
Early Gene ◽  
Single Image ◽  
Image Brightness ◽  
Image Intensity ◽  
Neuron Populations

High-resolution functional 2-photon microscopy of neural activity is a cornerstone technique in current neuroscience, enabling, for instance, the image-based analysis of relations of the organization of local neuron populations and their temporal neural activity patterns. Interpreting local image intensity as a direct quantitative measure of neural activity presumes, however, a consistent within- and across-image relationship between the image intensity and neural activity, which may be subject to interference by illumination artifacts. In particular, the so-called vignetting artifact—the decrease of image intensity toward the edges of an image—is, at the moment, widely neglected in the context of functional microscopy analyses of neural activity, but potentially introduces a substantial center-periphery bias of derived functional measures. In the present report, we propose a straightforward protocol for single image-based vignetting correction. Using immediate-early gene-based 2-photon microscopic neural image data of the mouse brain, we show the necessity of correcting both image brightness and contrast to improve within- and across-image intensity consistency and demonstrate the plausibility of the resulting functional data.

scholarly journals Single Image-based Vignetting Correction for Improving the Consistency of Neural Activity Analysis in 2-Photon Functional Microscopy

2021 ◽  
Author(s):  
Dong Li ◽  
Guangyu Wang ◽  
René Werner ◽  
Hong Xie ◽  
Ji-Song Guan ◽  
...  
Keyword(s):  
Neural Activity ◽  
Present Report ◽  
Activity Patterns ◽  
Quantitative Measure ◽  
Image Data ◽  
Early Gene ◽  
Single Image ◽  
Image Brightness ◽  
Image Intensity ◽  
Neuron Populations

AbstractHigh-resolution functional 2-photon microscopy of neural activity is a cornerstone technique in current neuroscience, enabling, for instance, the image-based analysis of relations of the organization of local neuron populations and their temporal neural activity patterns. Interpreting local image intensity as a direct quantitative measure of neural activity presumes, however, a consistent within- and across-image relationship between the image intensity and neural activity, which may be subject to interference by illumination artifacts. In particular, the so-called vignetting artifact - the decrease of image intensity towards the edges of an image - is, at the moment, widely neglected in the context of functional microscopy analyses of neural activity, but potentially introduces a substantial center-periphery bias of derived functional measures. In the present report, we propose a straightforward protocol for single image-based vignetting correction. Using immediate-early-gene-based 2-photon microscopic neural image data of the mouse brain, we show the necessity of correcting both image brightness and contrast to improve within- and across-image intensity consistency and demonstrate the plausibility of the resulting functional data.

Structural characterization of laser ablated epitaxial (Ba0.5Sr0.5)TiO3 thin films on MgO(001) by synchrotron x-ray scattering

1999 ◽  
Vol 14 (7) ◽  
pp. 2905-2911 ◽  
Author(s):  
Sangsub Kim ◽  
Tae Soo Kang ◽  
Jung Ho Je
Keyword(s):  
Thin Films ◽  
Early Stage ◽  
Lattice Parameter ◽  
Normal Direction ◽  
X Ray ◽  
X Ray Scattering ◽  
Surface Normal ◽  
Out Of Plane ◽  
Axis Parallel ◽  
Ray Scattering

Epitaxial (Ba0.5Sr0.5) TiO3 thin films of two different thickness (∼25 and ∼134 nm) on MgO(001) prepared by a pulsed laser deposition method were studied by synchrotron x-ray scattering measurements. The film grew initially with a cube-on-cube relationship, maintaining it during further growth. As the film grew, the surface of the film became significantly rougher, but the interface between the film and the substrate did not. In the early stage of growth, the film was highly strained in a tetragonal structure (c/a = 1.04) with the longer axis parallel to the surface normal direction. As the growth proceeded further, it relaxed to a cubic structure with the lattice parameter near the bulk value, and the mosaic distribution improved significantly in both in- and out-of-plane directions. The thinner film (∼25 nm) showed only one domain limited mainly by the film thickness, but the thicker film (∼134 nm) exhibited three domains along the surface normal direction.

Fabry-Perot Velocimetry Techniques: Is Doppler Shift Affected By Surface Normal Direction?

1984 ◽  
Author(s):  
David R. Goosman ◽  
Alan M. Frank, ◽  
Henry H. Chau ◽  
Norval L. Parker
Keyword(s):  
Doppler Shift ◽  
Normal Direction ◽  
Surface Normal ◽  
Fabry Perot

scholarly journals On The Effect Of Image Brightness And Contrast Nonuniformity On Statistical Texture Parameters

2015 ◽  
Vol 40 (3) ◽  
pp. 163-185 ◽  
Author(s):  
Andrzej Materka ◽  
Michał Strzelecki
Keyword(s):  
Texture Analysis ◽  
Texture Features ◽  
Unwanted Effect ◽  
Image Brightness ◽  
Fibrotic Liver ◽  
Image Intensity ◽  
Spatial Nonuniformity ◽  
Texture Parameters ◽  
Local Average ◽  
Average Image

Abstract Computerized texture analysis characterizes spatial patterns of image intensity, which originate in the structure of tissues. However, a number of texture descriptors also depend on local average image intensity and/or contrast. This variations, known as image nonuniformity (inhomogeneity) artefacts often occur, e.g. in MRI. Their presence may lead to errors in tissue description. This unwanted effect is explained in this paper using statistical texture descriptors applied for MRI slices of a normal and fibrotic liver. To reduce the errors, correction of image spatial nonuniformity prior to texture analysis is performed. The issue of sensitivity of popular texture parameters to image nonuniformities is discussed. It is illustrated by classification examples of natural Brodatz textures, digitally modified to account for inhomogeneities – modeled as smooth variations of image intensity and contrast. A set of texture features is identified which represent certain immunity to image inhomogeneities.

Valence band dispersion measured in the surface normal direction of CH3NH3PbI3 single crystals

2019 ◽  
Vol 13 (1) ◽  
pp. 011009 ◽  
Author(s):  
Jin-Peng Yang ◽  
Si-Xian Ren ◽  
Takuma Yamaguchi ◽  
Matthias Meissner ◽  
Li-wen Cheng ◽  
...  
Keyword(s):  
Single Crystals ◽  
Valence Band ◽  
Normal Direction ◽  
Surface Normal ◽  
Band Dispersion
Sign in / Sign up

Export Citation Format

Share Document