This is the README for ContactAngle, a simple and easy-to-use program
to extract contact angles from videos of liquid droplets on a surface.
The program is free and open source under a BSD license and will work
on various flavours of BSD, Linux and Windows (and possibly MacOS
X). It uses the [OpenCV] computer vision library for image processing
and the [wxWidgets] toolkit for the user interface.
It was originally created to optimise layer structures for digital
microfluidic (DMF) devices for work done at the [EMSG research group] at
the University of Edinburgh, Scotland, UK. The reason for writing it
was that we had no access to a commercial program that would reliably
and quickly extract contact angles from videos with hundreds of
frames.
The author is Daniel Gruber <daniel@tydirium.org>.
[OpenCV]: http://opencv.willowgarage.com/
[wxWidgets]: http://www.wxwidgets.org
[EMSG research group]: http://www.sircams.ed.ac.uk/emsg/index.html
How does it work?
~~~~~~~~~~~~~~~~~~~~
The program takes a very simple approach like the following:
- Read a frame from the video
- Binary threshold (convert it to black and white)
- Detect the shape of the droplet in an area close to where it touches
the surface
- Fit a parabola for each side and take the contact angle as the slope
of the function at the point where it touches the surface.
- Repeat for all frames in movie
This simple approach is robust and fast, but may not be as precise as
other algorithms that user a larger part of the image. However, it is
accurate enough for most purposes (did I mention it is free?).
For a description of how to use it, look at docs/Usage.html
Known problems and caveats
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- There seems to be a problem when running ContactAngle on *Windows
7*, however I do not have access to such a machine at the moment. If
you encounter problems, please send me an email.
- *Usable Video codecs*: by using the frame slider you can go back and
forth in the movie. However, due to limitations in the underlying
libraries, this only works on video formats where every frame is a
key frame (e.g. Motion-JPG), so you will have to convert your
videos, before you can use the program. For details, see
docs/Usage.html.
- It looks ugly on Windows (this could be changed, though).
- Accuracy might be less than some commercial offerings, but it should
be good enough for most purposes.
If you encounter bugs or would like a new feature not implemented yet,
please send me an email!
5 Downloads
~~~~~~~~~~~~
For the source code archives and precompiled binaries for Windows look
https://sourceforge.net/projects/contactangle/files/
6 Developers
~~~~~~~~~~~~~
See docs/Building_from_source.html
Enjoy!
