Implementation of the Midway Image Equalization

Guillemot, Thierry; Delon, Julie

doi:10.5201/ipol.2016.140

Cited by 12 publications

(14 citation statements)

References 6 publications

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“…The difference image DI defined in (8) requires the values I 2 (Ψ(x; p j−1 )), which are computed by bicubic interpolation [7]. Neumann boundary conditions are adopted for both, the gradient estimation, and the interpolation.…”

Section: Algorithmmentioning

confidence: 99%

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Improvements of the Inverse Compositional Algorithm for Parametric Motion Estimation

Briand¹,

Facciolo²,

Sánchez³

2018

Image Processing on Line

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In this work, we propose several improvements of the inverse compositional algorithm for parametric registration. We propose an improved handling of boundary pixels, a different color handling and gradient estimation, and the possibility to skip scales in the multiscale coarseto-fine scheme. In an experimental part, we analyze the influence of the modifications. The estimation accuracy is at least improved by a factor 1.3 while the computation time is at least reduced by a factor 2.2 for color images. Source Code The C++ source code, the code documentation, and the online demo are accessible at the web page of this article 1. Compilation and usage instruction are included in the README.txt file of the archive.

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Section: Algorithmmentioning

confidence: 99%

“…Note that contrast change may deteriorate the algorithm performance since it is not taken into account in (1). It can be handled by equalizing the input image contrasts, for instance using the Midway Image Equalization algorithm [8].…”

Section: Algorithmmentioning

confidence: 99%

Improvements of the Inverse Compositional Algorithm for Parametric Motion Estimation

Briand¹,

Facciolo²,

Sánchez³

2018

Image Processing on Line

View full text Add to dashboard Cite

show abstract

“…In this work, we extend the implementation proposed in [8] to a sequence of images, following the method proposed in [4]. The implementation is similar to [8], with the histogram of the frames modified according to the information of several images in a temporal window.…”

Section: Introductionmentioning

confidence: 99%

“…The implementation is similar to [8], with the histogram of the frames modified according to the information of several images in a temporal window. We describe two implementations: the sorting method [16], based on the sorting of the images intensities; and the histogram method, based on the matching of normalized cumulative histograms.…”

Section: Introductionmentioning

confidence: 99%

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Midway Video Equalization

Sánchez¹

2017

Image Processing on Line

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This article presents an implementation of the 'Midway Equalization' method for videos. This technique allows us to modify the image histograms so that they present similar luminances. We propose two algorithms: the first one based on histogram inversion and the second one on the sorting of images intensities. The former computes the histograms and then finds the contrast change functions by convolving the inverse histograms with a Gaussian function. The latter starts by sorting the pixels of each image by intensity; the temporal signals, composed of all gray levels of the same rank, are then convolved with a Gaussian function. In this sorting method, the resulting histograms are more similar and homogeneous. Nevertheless, the histogram strategy is faster and provides good results in general. The algorithms include a 'dithering' option for reducing quantization artifacts. The whole implementation depends on a single parameter, the standard deviation, that is used for Gaussian convolutions. The experiments show several examples, including the quantization artifacts that appear in some situations and the benefits of dithering. We observe that these artifacts are usually more important in the histogram method. Source CodeThe reviewed source code and documentation for this algorithm are available from the web page of this article 1 . Compilation and usage instruction are included in the README.txt file of the archive.

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Transport and Turbulence in Quasi-Uniform and Versatile Bose-Einstein Condensates

Gauthier¹

2020

Springer Theses

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Turbulence, motion characterized by chaotic changes in pressure and flow velocity, is a challenging problem in physics. However, its underlying properties are found to be universal and do not depend on the host fluid. Meanwhile, transport phenomena, irreversible exchange processes due to the statistical continuous random motion of particles, although being complicated from a microscopic point of view, can often be modelled quite simply by tracking macroscopic quantities of interest in the system. In this thesis, using atomic Bose-Einstein condensates, we study both these phenomena inside a quantum fluid using a highly configurable BEC platform developed to provide arbitrary dynamic control over the 2D superfluid system. Furthermore, the experiments are modelled using the Gross-Pitaevskii equation, the point vortex model and the hydrodynamic equations. After theoretical background and introduction to the apparatus, the technique of direct imaging of a digital micromirror device is described, which achieves the highly versatile and dynamic 2D potentials that facilitate the experimental studies described. Superfluid transport through a mesoscopic channel of tuneable length and width is next described. By investigating low amplitude oscillations and their dependence on the system parameters, a resistor, capacitor, and inductor model is used to model the transport. Surprisingly, the "contact inductance" of the channel at the reservoirs is a dominant effect for a significant portion of the parameter range. The resistive transport for high initial bias is also studied, showing an Ohmic resistive relationship over the broad parameter range. Next, the transport between two reservoirs initially prepared at different temperatures, but with similar particle number, was explored. Our 2D superfluid system, with hard-wall confinement, provides an ideal experimental system for the study of 2D quantum turbulence. The system is utilized to demonstrate the first experimental realization of large Onsager vortex clusters in the negative absolute temperature regime, through the injection of high energy clusters into the 2D superfluid. The clusters are found to be surprisingly stable for long time periods. The vortex cluster energy loss rate is studied while changing the system parameters, suggesting thermal damping is the dominant loss mechanism. The techniques and results presented in this thesis open up new avenues for the study of quantum fluids, be it by providing a concise atomtronic model for predicting superfluid transport or expanding the accessible parameters space available to fundamental studies of turbulence. The realization of negative temperature vortex distributions, long ago predicted by Onsager, open up the experimental study of the full phase-diagram of 2D vortex matter. The refinement of optical trapping techniques for BECs presents new and promising directions for future BEC experiments in configured potentials. This thesis is the culmination of many hours of work, to which a vast number of people contributed some ...

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Implementation of the Midway Image Equalization

Cited by 12 publications

References 6 publications

Improvements of the Inverse Compositional Algorithm for Parametric Motion Estimation

Improvements of the Inverse Compositional Algorithm for Parametric Motion Estimation

Midway Video Equalization

Transport and Turbulence in Quasi-Uniform and Versatile Bose-Einstein Condensates

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