Computer Vision - Detect More Than One Straight Edge with Best Edge Rake?

[ems1992]

Hello,

I am trying to use the Vision Assistant Advanced Straight Edge tool to detect rails on railroad tracks. Since I am predominantly looking for edges that extend the length of the image, I feel that using the edge rake tool is a good choice since it looks for edge matches all along the image. I have a question however, if I want to detect more than one rail at a time (more than one edge), how do I do this? The rake tool only offers first and best options meaning that the Straight Edges Requested dialogue is forced to one when I need this to be two (two rails). Does anyone know how to change this?

[Bob_Schor]

It is always helpful to include (at a minimum) the code that is giving you problems, as well as the version of LabVIEW you are using.

I looked in LabVIEW 2014, and could find no mention of an "Edge Rake" tool.  Are you using an Express VI?  I notice you mentioned the Vision Assistant Advanced Straight Edge Tool.  

Yes, it is an Express VI.

Rule #1 -- Express VI's are great for "playing with data" and seeing what LabVIEW can do.

Rule #2 -- Never use Express VI's to do anything serious.  They hide the capabilities of LabVIEW and don't let you "tweak" things.

There is a function, IMAQ Find Straight Edges 3, that I suspect the Express VI is using "under the hood".  It definitely has the ability to return multiple edges, as well as to limit the search for edges to a "region of interest" that you designate.  Give it a try.

Bob Schor

[ems1992]

Thanks for the information! Yeah, I saw that you could select as many edges as you wanted with the IMAQ Find Straight Edges 3.VI, but I was afraid that if the option was grayed out in the Express VI, then there must be some limitation in finding multiple lines with the rake tool. I already had the Express VI in a Diagram Disable, I was just using it to quickly test and visualize different edge parameters. I will give this a shot and post my results in a little while.

[ChristopheC]

You can only request multiple edges with the Best Hough Edge Rake, First Edge Projection and Best Edge Projection algorithms.

[ems1992]

Thanks, I tested the best edge rake with no avail yesterday so I'll have to try the best hough rake instead