ht_hist - Plot histogram of line confidences from ht output.
ht_hist [-o file] file
DESCRIPTION
ht_hist plots a histogram of the line confidence levels from the output file of
ht .
It gives a measure of how good the output is, which may reflect either a bad
choice of parameters for ht or poor quality edge input.
.PP
The confidence measure reflects the scatter of edge points associated with each
line segment in the direction perpendicular to that line. Outliers have been
removed by ht, so there can be no contributing edge pixels beyond a certain
distance (determined by the ht parameters used). This is then used to normalise
the confidence measure to lie between 0 and 1.
.PP
ht_hist also provides a mean confidence measure and the variance. These reflect
the number of false alarms that may have been produced, even if the correct
lines have been found with high confidence.
If no output file has been specified ht_hist will create a separate window in
which it displays the histogram, and produces the mean and variance values in
the window from which it was run. The size of the output window is controlled by
the environment variable PGPLOT_XGEOM, which is set to a standard width x height
geometry. To make the window in the same proportion as the hardcopy output on a
printer you should set this environment variable to
setenv PGPLOT_XGEOM 700x520
If an output file is specified by the -o option, then a postscript file will be
generated which can be sent to a laser printer.
OPTIONS
The only option for this program is an output option:
-o file name of output file. If not specified, output will go to a
separate Xwindow. You can generate postscript output by specifying an output
file.
P.Palmer@ee.surrey.ac.uk
September 1994