topic Re: ELLIPSE FITTING in Machine Vision

ELLIPSE FITTING

AndreaG47 — Wed, 25 May 2011 19:43:48 GMT

Hi! I'm trying to get the Ellipse fitting for a scattered data using the NonLinear Curve Fit, but I'm trying to use the general equation :A*x^2+B*x*y +C*y^2+D*x+E*Y+F=0 because the data present rotation from the original axes, but when I changed the Model, the parameters that I got were almost zero everytime that I've tried. I was wondering if there is another way to introduce the model to the VI or if there is another way to do that. Unfortunatelly I don't have NI Visual Detection module or the IMAQ, so I'm stuck in here. Can somebody help me please?

Re: ELLIPSE FITTING

JoseManuel — Fri, 27 May 2011 21:57:26 GMT

Hello Andrea. I recommend you to check the Fit ellipse VI: labview\examples\math\curvefit.llb. This example was developed for non rotated ellipsed. But you can try to implement your own model and modify the parameters to include an angle.

An general equation for an ellipse can be found in this page:

http://www.maa.org/joma/Volume8/Kalman/General.html

This is a good start point.

Regards.

José Manuel Vólquez Rodríguez

Applications Engineer, National Instruments México.

Re: ELLIPSE FITTING

toineroetman — Wed, 08 Jun 2011 07:32:39 GMT

Hello Andrea,

I have a vi from 8.6 maybe you can use it.

Please let me know if you improved it.

In the diagram are some pictures which formular i used.

Regards,

Toine

Re: ELLIPSE FITTING

leon88 — Thu, 31 Jan 2013 12:45:59 GMT

why your examples of Ellipse_X_Y_Length.vi can run?

Re: ELLIPSE FITTING

toineroetman — Fri, 01 Feb 2013 06:34:50 GMT

I added the 2 missing vi's.

Toine

Re: ELLIPSE FITTING

leon88 — Fri, 01 Feb 2013 08:46:25 GMT

Thank you.

I want to ask your ellipse can use to detect mango in picture?

Re: ELLIPSE FITTING

toineroetman — Mon, 04 Feb 2013 07:22:30 GMT

leon,

can you attach a picture? I can have a look.

Toine

Re: ELLIPSE FITTING

leon88 — Mon, 04 Feb 2013 14:41:38 GMT

Toine,

These are the mango picture.

Re: ELLIPSE FITTING

leon88 — Mon, 18 Feb 2013 15:15:43 GMT

Toine,

How? Can detect the mango picture?

Re: ELLIPSE FITTING

toineroetman — Tue, 19 Feb 2013 21:16:19 GMT

Hello Leon,

There are several ways in machine vision to detect the mango.

Main key is that there is a difference between the mango and the background.

Overlapping mango’s is more difficult then a single one.

If other light source or filter will enhance the difference between the mango and background it will help a lot.

Possible methods:

- Curve extraction

- Morphology

* Texture detection

* Object

- Shape matching

I think shape matching will work the best in this case. I do not have experience with that. So look around on the forum.

I added a morphology example to test your mango. Only the first picture this will work.

With kind regards, Toine

Thanks Toine, i want to ask your elllipse fitting can d...

leon88 — Wed, 20 Feb 2013 13:30:32 GMT

Thanks Toine,

i want to ask your elllipse fitting can detect the mango or cannot detect at all, or just cannot detect when overlaping or can detect just a single mango?

Thank you.

Re: Thanks Toine, i want to ask your elllipse fitting can d...

toineroetman — Fri, 22 Feb 2013 08:08:31 GMT

Hello Leon,

The ellipse fitting can not detect anything it uses the points found by the detection.

As i mentioned before a do not have a solution for DETECTION.

For a single mango it will be easier. The example a give will work with the THIS picture of a single mango.

There is no guarentee that it the detection will work with a other picture with a single mango.

It depends if the light, contrast, background, scale and so on will be the same.

Detection wil not be easy and needs to be tested with several different pictures.

With kind regards,

Toine Roetman