Pattern Match Search Rect Bug?

[Alvin6688]

Dear NI Community,

I have a question about Search Rect when using the Pattern Match VIs. When I add a bounding box as the rectangular search area for pattern matching, the results are sometimes different than if I leave the input unwired (i.e. search the entire image). It seems to change depending on the corner coordinates of my search area.

I've attached an example VI to more clearly show what I'm talking about. Three bounding boxes, varying only slightly, yet the match result is completely different. Is this something I'm doing wrong, or is it a bug?

Thanks in advance for your help,

Alvin

[BruceAmmons]

I know the pattern matching starts by doing a quick search for possible matches.  It checks at about 15 line intervals by default, if I remember correctly.  This parameter can be adjusted in the advanced settings.  For patterns with small details, it may be necessary to reduce the step size.

I am guessing it starts at the left edge of the ROI and increases by the step size.  Depending on where it starts, it can miss the pattern completely.

Bruce