Image Acquisitionand Proces

Image Processing 93
attributes. The VI has three outputs of interest: event, coordinates and other parameters,
which are populated as shown in Table 5.1.
TABLE 5.1
Event ROI Tool Coordinates [Array] Other Parameters [Array]
None Any NULL NULL
Click Cursor [0,1] xy position of the click [0,1,2] selected pixel intensity
Double click Any [0,1] xy position of the click [0,1,2] selected pixel intensity
Zoom [0,1] xy position of the click
[2,3] image xy center position
[0] new zoom factor
Draw Line [0,1] xy start point
[2,3] xy end point
Rectangle [0,1] xy start point
[2,3] xy end point
Oval [0,1] bounding rectangle start
point
[2,3] bounding rectangle end
point
Polygon [0,1] bounding rectangle start
point
[2,3] bounding rectangle end
point
[4,5], [6,7], [8,9] … vertices
Freehand [0,1] bounding rectangle start
point
[2,3] bounding rectangle end
point
[4,5],[6,7],[8,9]… vertices
Move Any [0,1] new position of the window NULL
Size Any [0] new width of the window NULL
[1] new height of the window
Scroll Any [0,1] new center position of image NULL
[0] bounding rectangle width
[1] bounding rectangle height
[2] vertical segment angle
[0] width
[1] height
[0] bounding rectangle width
[1] bounding rectangle height
[0] bounding rectangle width
[1] bounding rectangle height
[0] bounding rectangle width
[1] bounding rectangle height
In this instance, the user was able to use the draw vertices data returned in the
coordinates array, which was subsequently built into an array of clusters (each
containing the x,y pair of the pixels that were traced over). This allowed the user to
trace the path of the mouse (Figure 5.15).
As you can see in Figure 5.14, the coordinates array returns the start and end
point of the freehand draw operation, as well as the vertices of each point along the
way:
5.1.3 MANUALLY BUILDING A ROI: THE “ROI DESCRIPTOR”
It is often beneÞcial to programmatically deÞne ROIs, especially if there are
several objects of interest that are always in the same place within a series of