Matlab - Connect image's pixels with a curve -

Good morning, I will explain my problem. I pass through the pixel-point situations of a free surface cone of water in the tank I want to get the curve, so that next time I can work freely on the curve in an XY plane (for example, to compare 2 curves and subtract or subtract them).

I have tried a function with "Poly3" here:

  I = imread ('20jh1g2.jpg'); I = IM 2 BW (I); Imshow (i); [R, C] = Search (I); R = -R + size (I, 1); the figure; Plot (c, r, '.'); Wait; F = polyfit (c, r, 3); Plot (C): Maximum (C)), Polyval (F, (Min (C): Max (C)), 'Red', 'Linewid', 3);  

< P> But the approximation can be very large if the surface is "more complex" (high vibration).

Is there a function to connect each pixel to the next one? I use the "Spline function" Have read something about, but I did not understand how to use it and if this is the solution.

It is my interest An example of a vivid edge is:

How can I breed Matlab "absolutely" with an approximate approximate approximation (without bubbles)? I hope I have clarified my concept .

Thank you for your help!)