IMAQ Find Edge.VI does not return the edge if ROI width is >2100 pixels

[Massimo25]

When IMAQ Find Edge.VI  is used for finding a horizontal edge over a ROI wider than 2100 pixels, the VI returns an empty result (and no error). If the ROI width is reduced to 2000 pixel or less, then the VI returns the found edge. I tried to change the Edge Find parameters (e.g., decrease the number of lines), but it did not work either.

I am using Vision 8.6 and LabView 8.2.

Does anybody know what the problem is?

[muks]

can you post your image

[Massimo25]

The image is attached.

[Vivek_N]

Hello Massimo25,

I did not run into this problem when I tried it out. Could you try running the attached VI? Please let us know if it works for you.

[Massimo25]

Hi Vivek,

Thanks for your posting.

I tried your vi and it gave me the same problem. As I wrote in the previous posting, the problem appears to be related to the width of the ROI. Referring to the image I posted earlier, the edge I am interested in is the (almost) horizontal line that divides the dark region from the brighter one (the vertical lines you can see in the brighter region are not the edges I am interested in). Please try the attached vi. Try with a ROI (which includes the edge of interest) that is as wide as the image and with a ROI that is only 1000 pixel wide. Please let me know if you see the same issue.

Thanks,

Massimo

[avasil]

Was this resolved? I tried to run this on my computer and have similar issues. The issues are showing up in a different application but this discussion narrows down the issue. In my application, the IMAQ Find Edge works randomly. Sometimes I do get the Straight Edges array with data and sometimes I do not.

Here are some more details.

If you monitor the image that is displayed after going throuh the IMAQ Find Edge.vi (set the display options for search Area, Seach Lines, Edges Found and Show Result to TRUE) then the image shows that all the edges are found, but somehow the results are not populated in the Straight Edges array.

I am using

LV 8.6

Vision Acquisition SW 8.6

PC

Lenovo ThinkCentre

Win XP SP2

Intel Core 2 Duo E6850 @3GHz. 3 G RAM

[avasil]

One more detail. My images are actually smaller than the original posted for this discussion, but the effect is random. Image size is 350X420

[DjDaveNI]

All,

The IMAQ Find Edge VI has an optional input called “Line Fit Options”. The reason why you return an empty resultant array of straight edges (and no overlayed edge result on the resultant image) is that a line could not be best-fit through the points that were identified by the LV_FindEdge vision function. Modify and adjust the “Line Fit Options” parameters in the IMAQ Find Edge VI to meet the requirements for your image.