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FOLKI

GPU acceleration of particle image velocimetry

Alex Ames

What’s the idea?

Given an input image pair, determine the velocity vector field using a recursive gradient-based image deformation algorithm based on Lucas-Kanade optical flow, adapted for the unique illumination characteristics of PIV images.

FOLKI (flot optique Lucas-Kanade itératif) algorithm

  • Read image data (.tif, .png, other uncompressed formats?) from given filepath
  • Read metadata (interframe time, pixel spacing) from configuration file
  • Normalize/filter/clean image data
  • Resample image at n ∈ N resolution levels, dividing the resolution by 2 each time
  • Starting at the lowest-resolution image, determine & upsample displacement fields:
    • Compute spatial intensity gradient of initial image
    • Compute 2x2 minimization matrices H for each pixel
    • Iteratively:
    • Compute deformed image intensity from prior displacement estimate u₀
    • Compute RHS vector c = (ΔI - ∇I u₀) ∇I
    • Solve 2x2 system u = H⁻¹c for each pixel
    • Upsample estimated displacement field to match the resolution of the next level

How is it run?

A working Julia installation is required: download the latest release for your platform here. If you'd rather not install anything, you can register for a JuliaBox account, which gives you free access to a remotely-managed Julia environment.

Several additional packages must also be installed; this is done by entering the Julia command-line and typing Pkg.add("packagename"). To be sure everything has been installed correctly, type versioninfo(true) in the Julia prompt. The required packages are:

  • Images
  • ImageView
  • Interpolations
  • Plots
  • Glob

Once the environment is properly configured, the code can be run by navigating to the scratch/ directory and running include("repl.jl") from the Julia prompt.

First Commit

11/04/2017

Last Touched

almost 2 years ago

Commits

19 commits

Requires:

Used By: