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Release Notes
 

  

 
LineFinder - 41

This tool finds multiple lines using a traceline. The trace comb can be rectangular, circular or radial.

LineFinder is a very powerful tool requiring training and experience to take full advantage of all its features. To the right a rectangular tracecomb with 21 lines locates a line. The fitted points are shown with green circles and the line is visualized in red.

See Locate detail with two LineFinders for an example of use.


Setup

Reference - Reference system selection

Trace lines - describing the edge search area 

The user can select traceline with the following shapes

  • Rectangular
  • Circular
  • Radial

The shape selection is defined by the object.

The ROI can be managed by the buttons

  • Paste - paste the ROI from the image to the scorpion clipboard
  • Copy - copy the ROI to the image from the scorpion clipboard

Point & Click Clipboard Support

The rectangular ROI can be defined by four points. The two first points define the length and direction of the trace comb. The other points define the width of the trace comb.

The circular and radial ROIs are defined by the two points of a line. The first point defines the origo / center. The second point defines the center of the tracecomb. To edit the width or length of the trace comb - use the control fields of the tool.

With the rectangular ROI a line will define the center trace line - thus the length and the direction of the trace comb.


One point will change the center point for all ROI variants


 

Rectangular trace lines

  • Center-x - center x of search comb
  • Center-y - center y of search comb
  • Angle - angle of search comb
  • Length - length of search comb
  • Width - width of search comb
  • Number of trace lines - Number of trace lines in search comb
  • Trace line width - width of each trace line. See Edges and contours
  • Sample step (pixels) - step size between samples.  See Edges and contours

Circular trace lines

  • Center-x - center x of search comb
  • Center-y - center y of search comb
  • Center angle - center angle of circle sector
  • Radius mid point - distance from center to middle of search comb
  • Radial length - width of search comb
  • Angular width (degrees) - lenght of search comb, an angle measure
  • Number of trace lines - Number of trace lines in search comb
  • Sample step (pixels) - step size between samples.  See Edges and contours

Radial trace lines

  • Center-x - center x of search comb
  • Center-y - center y of search comb
  • Center angle - center angle of circle sector
  • Radius mid point - distance from center to middle of search lines
  • Radial length - length of search lines
  • Angular width (degrees) - width of search comb, an angle measure
  • Number of trace lines - Number of trace lines in search comb
  • Sample step (pixels) - step size between samples.  See Edges and contours

Trace line samples dialog - a helper window to set trace line filter parameters and thresholds

  • Middle - show the middle traceline
  • Middle+edges - shows the first, middle and last traceline
  • Selection - show the selected tracelines
  • Line indices - traceline selection
    • example: 2,3,12-15
    • example: 1 3 5 7

  • Show trace line popup - activates a modeless traceline window


Example tracelines - Middle+edges is selected


Advanced

Filter

  • Smooth base - 3 is normally a good value
  • Smooth counter - 1 default - given i pixels
    • The smoothing increasing with higher values
  • Differentiation
    • 0 - give threshold
    • 1 - 1. order differentiation - the derivative - default normally used
    • 2 - 2. order differentiation
  • Mode - Peaks are default. Threshold is only used when Differentiation is set to 0.

More information - see Filter parameters

Note : Combining 2. order differentiation and polarity are used to find the center position of light or dark stripes

Edge Detection

  • Polarity - Dark to light | Light to dark | All transitions
  • Threshold - value lower values means more sensitivity

Line Fit

  • Fit tolerance - points outside tolerance is not accepted
    • Tolerance given in pixels or reference coordinates
    • More information - Line fit.
  • Minimum number of points - minimum number of points fitted to circle to be accepted

Search parameters

  • Search risk (PPM) - 1 default - a lower value will perform more iterations
  • Max search time (sec) - limits the search in second - default 10

Results

  • Sort results by - Gradient | Fitted Points | Line Lengths | Line Centers
  • Inv - will invert the sorting direction

Resulting reference system

  • Rotate - the center and angle of the best line is used as outgoing reference system. Uncheck to ignore the line angle


Constraints

Edge points to keep from each search line - One can filter on position and / or gradient

Position - All | First | Last

No - Number of points to keep pr line

Gradient - All | Largest | Smallest

No - Number of points to keep pr line

Note : The filters are very powerful - one can easily pick the first line by selecting Position = First and limit No to 1 or 2

The following constraints are used to reduce the number of lines reported as results. Best practice is to use the constraints to add properties of the inspected objects. This will make the processing go faster and to be more reliable.

Max number of lines

Active - Enable line number filter

Max - max number of lines to report as a result

Line Length 

Active - Enable the filter to remove lines not meeting the length criteria

Min - minimum accepted length in reference coordinates

Max - maximum accepted length in reference coordinates

Gradient 

Active - Enable the filter to remove lines not meeting the gradient criteria

Min - minimum accepted gradient  in reference coordinates

Max - maximum accepted gradient in reference coordinates

Absolute value - check to ignore edge slope direction

Coarse line angle filter - use to reduce processing time - accuracy it not very good - set value with margins 

Active - Enable the filter to remove lines not meeting the angle criteria

Min - minimum accepted angle

Max - maximum accepted angle

Line angle  - with good accuracy 

Active - Enable the filter to remove lines not meeting the angle criteria

Min - minimum accepted angle

Max - maximum accepted angle

Line angle  - with good accuracy 

Active - Enable the filter to remove lines not meeting the angle criteria

Min - minimum accepted angle

Max - maximum accepted angle

Max Gap - missing points on a line to reject a line

Max - number of missing points accepted


Visualisation

BestLine The line deemed first first by the sorting specification
BestLineFat The same line, drawn thick
EdgePoints All edge points within the ROI
FittedPoints Edge points fitted to lines
Lines The lines found by the tool
LinesFat The same lines, drawn thick
ROI Region of interest
Trace lines Search lines used


Results

Number of lines

The number of lines found

Line[n].p.x

Line n starting point

Line[n].p.y

 

Line[n].v.x

Line n vector

Line[n].v.y

 

Center[n].x

Center position of line n

Center[n].y

 

Length[n]

Length ov line n

Angle[n]

Line angle, line n

Gradient[n]

The average gradient for the fitted tracelines

Line fit[n]

The RMS value of the line-fit for a line 

Trace line span[n]

Number of tracelines between first and last fitted point

Number of points[n]

The number of fitted/accepted points on the line 

Widest gap[n]

The widest gap (no fitted points) on the line

Note: <n> ranges from 1 to 15


ExecuteCmd support
- more information executeCmd

Command

Parameters

Return values

Comments

Set Object=ROI;Value=<point/line/polygon> ok,res Sets the tool's ROI. See Copy/paste ROIs for details.
Get Object=ROI ok,<line/polygon> Current ROI as rectangular, closed polygon

More examples - Example 33 - Changing the ROI of a tool

 

Scorpion Vision Version XII : Build 646 - Date: 20170225
Scorpion Vision Software® is a registered trademark of Tordivel AS.
Copyright © 2000 - 2017 Tordivel AS.