find a circle

Posted by Clausalism* on Apr 01, 2011; 7:16am
URL: http://imagej.273.s1.nabble.com/find-a-circle-tp3684935.html

Hello,

i'm searching for a macro in imagej to automaticly find a circle in a given image. This Image shows a orb beeing hit by a laserlight:

Now i want the program to find this orb by itself. My idea was to use an macro comparable to "analzye particles - ellipse". Although this one doesn't work, because the orb is bright at his upperside and dark on his downside! So imagej never gives the complete circle back, but an ellipse cutting of an part of the orb.
So i ask you, if you would now any plugin that can find the best fitting circle in an image if i tell him how big the circle ist?

Thank you

ps: i also tried to alter the image before fitt the ellipse by "spilt colour-channels" "treshold" and others, but because of the great overexposure of the background, nothing really did work for me)