Contours
Contours
The purpose of this option is to all the contours satisfying a paritcular
intensity level and minimum length to be located within a window. Unlike
[E Locate edge in window], more than one contour may be found, but the data
is not available for inclusion in a file.
Find contours on which buffer ?
This entry specifies the buffer containing the image on which the contours
are to be located. The selected buffer will be made the current output
buffer until the contour location begins. If the buffer is in extended
memory, then it will be copied to buffer 0.
Plot contours on which buffer ?
As each contour satisfying the length criterion is found, it will be
plotted out on the buffer specified. This buffer is not erased prior to
starting the contour location, and is made the current output buffer during
the location procedure.
Contours in Window or Screen ?
The contours may be located in a subwindow, or the entire frame buffer.
Window Specification: Region containing contours
If a window is chosen, then sections of the contour falling outside the
window will not be included. Control over the window selection is in the
normal DigImage manner. Further details are available from [H Help] within
the window selection menu.
Threshold value ?
The contours being searched for are specified by a threshold value.
DigImage will position the contour at pixels with an intensity less than or
equal to this threshold, where their neighbour is greater than the
threshold.
Plot contour with what intensity ?
As they are located, the contours will be plotted to the required frame
buffer using the intensity specified by this field.
Minimum number of points in edge ?
The contours found by DigImage may be filtered on the basis of its
length. This entry specifies the minimum length the contour may have: if a
contour is located with a shorter length, then it is disregarded and not
plotted.
Smooth over how many pixels ?
Once the pixels belonging to a contour satisfying the minimum length have
been found, DigImage provides the option of passing these points through a
low pass filter before outputting them onto a buffer. The low pass filter
operates by computing the average position of the pixel and its neighbours.
This entry specifies the number of pixels to be included in this average. A
value of zero will suppress the smoothing. If a nonzero value is specified,
the averaging will utilise an odd number of pixels (the odd number greater
than or equal to the specified value). The smoothing operator looks after
both closed and open contours in a rational manner. Note that this form of
smoothing will tend to decrease the area contained within a closed contour;
this may be significant for very small closed contours.
Following contours...
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DigImage User Documentation
Stuart Dalziel,
last page update: 19 February 1996