ContactAngle - extract contact angles from videos and images
This is the site for ContactAngle, a simple and easy-to-use program to extract contact angles from videos of liquid droplets on a surface.
1 News
15/3/2011: The project is now hosted on sourceforge
24/1/2011: First public release of version 0.2. Please have a look at the Release Notes.
2 About the program
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>.
3 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 here.
4 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 Usage.
- 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 here.
6 Developers
See Building from source.
Date: Thu Apr 14 17:38:32 BST 2011