Detecting partial circles in images

[Mariahnova]

I was really thinking more about the centering of the wheels instead of the definition of a partial circle which is what I think you are describing but I'm not sure.

[Yesh]

Marianhova

Yes you can convert the code into labview. Simply right click

on the vi and choose open front panel. This will open a new VI.

The color of your express VI changes to yellow. Just go to edit and 

choose undo change attributes. There you go you will see the entire

code before you.

[Richard_M]

David,

You define the centre of the two circles, and they can be different. Clearly, if you're not sure where in the image the circle you're looking for is the inner circle needs to be small and the outer large. If the circle you're looking for is small you need to ensure it's in the centre so the inner search circle is inside it. 

Another way would be to convert it to binary and search for blobs. You can search the image for a circular 'blob' which gives the centre. This could be used for the edge detection as it may be a more accurate method.

[chilly_charly]

@Yesh and Mariahnova

If you are using LV 9.0 (and up), you should have copied the snippet provided in my first post to the BD of your vi. Then a dble-click on the Vision assistant icon would have opened the assistant, showing the code behind.

When prototyping an image analysis application, you don't need to open Vision Assistant independently and then go through the process of asking VI creation, defining file destination and so on. A more direct and much simpler solution is to use the assistant from within the VI. The assistant is accessed from the bottom-right of the Vision palette : Vision express.

Of course, as usual, once everything has been defined, some cleaning will be required after converting the express VI. This will save processing time and memory footprint.

[chilly_charly]

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Mariahnova a écrit :

I played with the edge detector and the spokes confused me. The documentation is pretty weak on this function.

Anyway, is it possible to programatically control the location of those spoked wheels? I am brand new at this, but I am assuming that once you have defined a script in the assistant you can convert this to regular LV code like any other Express vi. Is that the case?

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The Help for IMAQ Vision is located in the Help > NI Vision for LabVIEW Help...

As shown in the extract below, the documentation is accurate and pretty well developped (see the slider on the right side ?)... once you know where to find it ! You should go through the whole Help at least one time to learn all the concepts and possibilities of IMAQ Vision.

[whs]

Hi,a similar problem I am facing now is about the shape detecting as in the image attached. 

The black partial moon-like shape is what I am interested in. The right curved edge is a partial circle, and the left curved is a partial ellipse with the minor axis the same length as the radius of the right partial circle. A series of such images are detected. How do I get the radius of the partial circle and the major axis of the partial ellipse? Any help would be appreciated.

whs

[whs]

The black partial moon-like shape is what I am interested in. The right curved edge is a partial circle, and the left curved is a partial ellipse with the minor axis the same length as the radius of the right partial circle. A series of such images are detected. How do I get the radius of the partial circle and the major axis of the partial ellipse? Any help would be appreciated.

whs

[whs]

Any advice?