Chapter
4
Reference Manual
IVC-2D
130
©
SICK AG • Advanced Industrial Sensors • www.sick.com • All rights reserved
Circular
Internal Perimeter
This tool traces the internal contour of an object and is similar to the tool 'External Perime-
ter'. Return values are the center of gravity coordinates of the area inside the contour. The
operation can be described as follows: First, the tool scans the gray values along a user
defined line to find a point on the internal contour of the object. Beginning at the starting
point of the line the first change in gray values that is greater than a defined threshold is
indicated as a point on the contour. Note that the line must be drawn from left to right to
achieve correct results. Then the tool traces pixels with the required change of gray value
starting at the found point on the contour. To make the algorithm more robust it is neces-
sary to define a range on the gray scale with an upper and lower threshold.
Recommend steps to set up the input parameters:
1. Double-click the input field for
Relative threshold
and double-click the appearing
button. This opens an interactive window. Set the line in the image with the left mouse
button. Remember that the line must be drawn from left to right. Modify the
Relative
threshold
with the slider on the left side until a point on the contour is found. This point
is marked with a cross. Close the window.
2. Double-click the input field for
Gray low
or
Gray high
threshold and double-click the
appearing button. This opens an interactive window. Modify the lower and upper
threshold with the slider on the left side until the internal contour of the object is
traced completely. Control the traced contour in the image and make sure that the
traced contour is robust against small variations of the upper and lower thresholds.
The results of this tool can be used for the following tools:
Circular perimeter ROI
Circular analysis
Check circular shape
Input Parameters
01 = Source bank
Image bank containing the image to be processed.
02 = Start point X
X coordinate for start point of line.
03 = Start point Y
Y coordinate for start point of line.
04 = End point X
X coordinate for end point of line.
05 = Endpoint Y
Y coordinate for end point of line.
06 = Relative threshold
Required absolute change of gray value to find contour
points.
07 = Gray low
Minimum gray value of pixels along the contour.
08 = Gray high
Maximum gray value of pixels along the contour.
09 = Angular interval
Resolution for re-sampling the contour in degrees.
10 = Destination bank
Image bank in which to show the image with colored
contour and calculated centroid of the internal area.
