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Making measurements within acquired video?

Hi everyone! I have an interesting problem and was hoping someone could help guide me down the correct path. Currently, we are using Labview to capture video (.avi) in one of our experiments. Provided the video, we would like to be able to make measurements at different points in time. Specficially, we would like to measure the diameter of a circle at different points in time as it grows in size. The diameters will likely be in the range of 1-5 mm. Is there any kind of post processing method that could help us? I am pretty new to labview so I am not too familiar with the possibilities, any help would be greatly appreciated!



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Check out IMAQ.  It is a very complete set of machine vision tools to handle just about anything.  If you don't have a budget for IMAQ (or a site license if you are at a school or university), you will need to do it yourself.  The steps are roughly as follows:


  1. Get a single frame of the video.  This may be more or less difficult, depending upon the video format and the APIs available to you from your camera manufacturer.
  2. In this single frame, apply image processing techniques (e.g. check out this Stack Exchange answer for finding a circle)
  3. Go to the next frame and repeat.

If you don't have IMAQ, be prepared to write some code.  The algorithms for finding circles in images are fairly well documented in many places, and you can implement them in LabVIEW, but you may need to go to a lower level than you are used to.  If this happens, just go for it.  Or convince your supervisor/professor to get IMAQ Smiley Wink.


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