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Optical Flow file wizard

Project description


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Converts Optical Flow .flo files to images .png and optionally compiles them to a video .mp4 via ffmpeg



Easiest option to install flowiz is to grab the latest package from PyPI repo

pip install flowiz -U

pip + Github

Alternatively you may install the package directly from github repo

pip install git+

Build yourself

Or you can run to build it yourself locally

git clone
cd flowiz
python install --user

Make sure you have requirements installed along with an ffmpeg to compile a video. requirements.txt contains latest working versions of this package. Feel free to use pip-upgrader.

pip install -r requirements.txt
apt install ffmpeg 
# pacman -S ffmpeg


Package can be used both from the command line and python script.

Command line usage

The following script grabs .flo files from ./demo/flo/ directory and converts into .png saving in the same directory

python -m flowiz demo/flo/*.flo

You can pass output directory for .png images via -o or --outdir parameter

python -m flowiz demo/flo/*.flo --outdir demo/png/

You may compile converted .png images into a 24 fps .mp4 clip by passing -v or --videodir parameter with a video output directory (without a filename)

python -m flowiz demo/flo/*.flo -o demo/png --videodir demo/mp4

Pass -r or --framerate parameter to control the framerate of compiled video

python -m flowiz demo/flo/*.flo -o demo/png -v demo/mp4 --framerate 2

Python usage

Relevant python code is available in demo/test.ipynb notebook. Here's an excerpt:

import flowiz as fz

files = glob.glob('demo/flo/*.flo')
img = fz.convert_from_file(files[0])


In case you need to visualize U V channels separately from your numpy floArray:

uv = fz.convert_from_flow(floArray, mode='UV')
axarr[0].imshow(uv[...,0], cmap=plt.get_cmap('binary'))
axarr[1].imshow(uv[...,1], cmap=plt.get_cmap('binary'))


GUI usage

Beta version of the flowiz graphical user interface is now accessible via flowiz.gui package. It is packaged using ChrisKnott / Eel and available via default web browser. To run the GUI simply type:

python -m flowiz.gui

Upon launching the web app, drag and drop or choose .flo file(s) using the open file dialog. Files will be converted using the python backend and placed in a temporary directory flowiz/gui/web/guitemp. Upon every session temporary directory will be emptied to avoid unnecessary polution.

Mockup of the GUI is available at

Demo Video


$ python -m flowiz -h

usage: [-h] [--outdir OUTDIR] [--videodir VIDEODIR]
                    [--framerate FRAMERATE]
                    input [input ...]

positional arguments:
  input                 Input file(s). (e.g.: __ ./demo/flo/*.flo)

optional arguments:
  -h, --help            show this help message and exit
  --outdir OUTDIR, -o OUTDIR
                        Output directory path. Default: same directory as
                        [.flo] files. (e.g.: __ -o ./demo/png/)
  --videodir VIDEODIR, -v VIDEODIR
                        Compiles [.mp4] video from [.png] images if parameter
                        is passed. Parameter requires video output directory
                        path without a filename. (e.g.: __ -v ./demo/mp4/)
  --framerate FRAMERATE, -r FRAMERATE
                        Frames per second of the video. (e.g.: __ -r 2)


The library is based on Midlebury's Vision Project MATLAB code: Original credits to Daniel Scharstein (C++) and Deqing Sun (MATLAB)


Q: But what kind of name is flowiz?
A: The kind you choose when flowkit, flowtools, flowlib, flowlab are already taken.

Q: Future work?
A: Some of the To-Do features are listed below with no determined timeline. If you'd like to contribute with the said features or something completely new, you may fork it and issue a pull request.


  • Ported from Matlab flow_code
  • Project is available on PyPI
  • GUI
    • Improve Front to Back-end throughput performance

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