Image calibration

[Veena]

Hi...can anyone tell me how to go about doing the following image calibration steps done?

I have an image that is grabbed using IMAQ PCI 1424 card using dalsa camera. My image consists of a plain black one with white intensity spots placed at equidistant on the image(something like the one u see in the calibration grid except that the spots here are white and the background is dark).I have to specify a uniform grid around each one of the spot so as to make a selection of the spot). Now for each grid I have to find the centroid. and my final output should be an 2-d array which is the centroid of each of the grids.
How can I go about getting this done?
I use LabVIEW Ver. 6.0 and IMAQ vision 6.0.

Veena..

[Alberto]

Hi Veena,
first you have to use the threshold function to get a binary image, this shouldn't be difficult since you have white spots on black surface.
If the result image has only your spots well outlined, you can directly use the IMAQ Find Circles function to get informations of all the circles contained in your image. This returns an array of clusters of circles dimensions, radius and area.
If you want to select only some spots to be detected you have, after thresholding, add ROIs to your image and apply the IMAQ Find Circles only to the extracted image from ROI.
Keep in mind that the IMAQ Find Circles lets you set the min and max radius of the circles to be detected, use this parameters to exclude small disturbing parts on your image; second, this function wor
ks correctly only for circles that have a radius less than or equal to 256 pixels.
Good luck,
Alberto

[Veena]

hi...I will give a try to what u have suggested...
can u tell me how to find the centroid of the individual grids...any idea?
Veena.

[Veena]

Hi Alberto,
The solution works, only thing is that I cant understand how does FindCircles function work?Since I need to get the output in an ordered form from top left corner circle to bottom right one (left to right)
How can I get this done and not ramndom numbering of the circles found.
Any suggestions?
Veena.