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The SingleLineFinder - SLF - tool is a tool used to find single lines.
A second pass is made with tracelines normal the lines can improve lineprecision
in sub-pixel resolution systems.
The SLF has a edgepoint mode where no line is calculated.
- In this mode it can be used to convert laserlines into
3D images or point cloud.
- In Stereo Vision systems Locate3D can combine and sort
the edgepoints to real 3D coordinates
Setup
Reference - Reference system selection
Trace lines - describing the edge search area
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 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. 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.
- Two-pass line fit - add a second pass to fit the line,
adjusting the search lines to be approximately perpendicular to the
line. This improves the line fit accuracy.
- Center-x - center x of search comb
- Center-y - center y of search comb
- Width - width of search comb
- Length - length of search comb
- Angle - angle of search comb
- Count - number of trace lines
- Distance - distance betwees trace lines
- Width - width of each trace line. See
Edges and contours
- Step (pixels) - step size between samples. See
Edges and contours
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. An additional choice is Curve correlation - see below.
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
- Percent threshold - dynamic threshold based on values from
current traceline
- Threshold - (if not percent) value lower values means more sensitivity
- Min threshold - (if percent) minimum percent value used
Correlation search
To search for a known intensity curve rather than an edge, the
correlation search may be helpful. You can select a step or a pulse curve
form, or edit your own shape.
- Step - a step. You can modify leading and trailing edges, and
the slope length
- Pulse - a pulse. You can modify leading and trailing edges,
the slope length and the pulse width
- Custom - create your own shape in the editor described below
- Minimum Std for match - minimum Std (or variation) in image
for a match to be considered
- Use normalized correlation - normalise by removing mean and
equalising Std in both image and curve
Shape editor
The curve shape is edited as a sequence of samples (space delimited). The
defined center is where the edge point will be reported in the search.
Advanced
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
Fit string results
- Create string with fitted points polygon - create a polygon of
fitted points for external processing
- Create string with fitted point distances from line-
create a polygon of fit distances for external processing
- Interpolate/extrapolate missing points - estimate values if
some points are missing in the fit process
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 | Distance | Separation
- Inv - will invert the sorting direction
Status
- Tool fails if no line is found - means that tool returns status = 3
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
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
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
Max Gap - missing points on a line to reject a line
Max - number of missing points accepted
Visualisation
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EdgePoints
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All edge points within the ROI |
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FittedPoints
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Edge points fitted to the line |
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Line
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The line deemed first first by the sorting specification |
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LineCenter |
Center position of line |
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OrigEdgePoints
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First pass edge points within the ROI |
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OrigFittedPoints
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First pass edge points fitted to the line |
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OrigLine
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First pass line found by the tool
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OrigLineCenter |
First pass center position on line |
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OrigROI
|
First pass
region of interest |
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OrigTraceLines
|
First pass
search lines used |
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ROI
|
Region of interest |
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Trace
lines
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Search lines used |
Results
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Line.p.x
|
Line starting point |
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Line.p.y
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Line.v.x
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Line vector |
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Line.v.y
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Line.q.x
|
Line end point |
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Line.q.x
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Line.Length |
Line length |
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Line.Angle
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Line angle |
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Center.x
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Center position of line |
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Center.y
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Length |
Length ov line (again) |
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Angle |
Line angle, line (again) |
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Line angle |
Directed line angle |
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Gradient |
The average gradient for the fitted tracelines |
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Line fit |
The RMS value of the line-fit for the line
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Trace
line span |
Number of tracelines between first and last fitted point |
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Number
of points |
The number of fitted/accepted points on the line
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Widest
gap |
The widest gap (no fitted points) on the line |
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Tracelines |
Number of tracelines used |
ExecuteCmd support - more information
executeCmd
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Command
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Parameters
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Return values
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Comments
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Set |
Object=ROI;Value=<point/line/polygon> |
ok,res |
Sets the tool's ROI. See Copy/paste
ROIs for details. |
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Get |
Object=ROI |
ok,<line/polygon> |
Current ROI as rectangular, closed polygon |
See also - Example 33
Changing the ROI of a tool |
