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Re: [APD] web cam

Doing the Gaussian blur is reasonable in trying to avoid any 
mis-registration problems due to motion, but the downsample would not be 
needed, imho.  The white balance is just a camera calibration, and would be 
needed for any type of algorithm development.  Assuming a fixed camera 
position and a stable camera calibration , you'll get a filtered image 
which will combine information from many pixels into a single pixel.  You 
could hand segment the image into 'uniform' regions that should only 
contain one plant type.  If the area is truly uniform, and depending on the 
kernel size for the Gaussian blur, you should wind up with a small 
distribution of pixel intensities.  if you dont, then the kernel needs to 
be bigger (5x5 or maybe even 7x7)  or the problem may not be feasible.  If 
the distribution varies spatially within a 'uniform'  plant section, it 
indicates that the color intensities are dependent upon the orientation of 
the leaves, other reflections from the tank, etc, complicating the 
diagnostic process.  So lets say the distribution is nice and tight.  Then 
multiple measurements need to be made over time.  Variance in the 
measurements or distribution may be an indicator of plant stress, or simply 
changing conditions, eg watre changes, fertilizer dosing, CO2 changes 
etc.  You're simply looking at a single measurement for subtle changes 
which may be highly dependent upon the water chemistry and parameters.  If 
you were talking multiple wavelengths then perhaps you could build more 
robustness into the system, but for a simple color or IR camera, I'd be 
surprised.  In my research I have not found any papers on using single band 
imagery for this type of problem.

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