Chapter
4
Reference Manual
IVC-2D
92
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SICK AG • Advanced Industrial Sensors • www.sick.com • All rights reserved
Edge
Find Mean of Edges
This tool performs a linear fit on certain pixels in the image. Return values are the mean
position on the fitted line and the deviation from the line of the found pixels.
The pixels for the fit are generated by a gray value evaluation either along selected co-
lumns or selected rows. Beginning at the starting point of the column or row the first pixel
showing a change of the gray values that is at least of the amount of a user defined value
is indicated. In general the direction of evaluation is either along the columns or the rows
and is selected by an input parameter.
This tool requires a rectangular non-rotated ROI from a previously performed step. Note
that only ROIs generated by the ‘ROI Rectangle’ tool can be used. Do not use ROIs from
any other ROI tool. Only the columns or rows inside the ROI are considered.
To speed up processing time it is possible to select how many columns or rows inside the
ROI that should be evaluated. The input parameter
Scan interval
in pixel defines the
equidistant gap between each column or row in pixels. The precision of the linear fit is
increased with the number of columns or rows.
After the gray value evaluation is performed further conditions select the pixels that are
considered for the linear fit. To ignore a single outlier it is possible to allow a maximum
distance from the next found neighbor pixel. To ignore connected pixels it is possible to
define a cluster build with a minimum number of connected pixels. Clusters of this size and
a distance of more than the allowed maximum distance to the next cluster are ignored for
the fit.
Double clicking the input field for the
Threshold
parameter and double clicking an appea-
ring button opens a larger image. This new window allows setting of the
Threshold
parame-
ter and displays the found pixels and the fitted line in the image.
The tool returns the coefficients of the equation for the line that represents the edge. The
equation is on the form y = kx+m.
Input Parameters
01 = Source bank
Image bank containing the image to be processed.
02 = ROI definition step
Step number where the ROI to use was created.
Note that only ROIs generated by the 'ROI rectangle'
tool can be used.
03 = Analysis direction
Direction of the evaluation to generate pixels for the fit.
The choices are:
Left -> right
Down -> up
Right -> left
Up -> down
04 = Scan interval
Define gap between equidistant spaced columns or
rows in pixels.
To evaluate each column (row) type in 0.
05 = Threshold
Amount of the minimum required change of gray
values.
06 = Pixel distance
Maximum allowed distance in pixel from next found
neighbor pixel.
07 = Average pixels
Allows to average gray values over up to 16 pixels
along the scan direction.
08 = Min connected transitions
Defines minimum required number of connected pixels
with the allowed distance from next neighbor pixel
(combination with the input parameter Pixel distance).
09 = Destination bank
Number of the destination bank in which to display
source bank, selected pixels and fitted line. Make sure
that Destination bank is different from Source bank.
