If things go wrong with ht , this package enables you to zoom in on an area of the image and see which edge points are providing support for the hypothesised line segments.
If no output file has been specified ht_plot will create a separate window in which it displays the edge points and line segments. The size of the plot is automatically scaled to fit within the window (or page in postscript) without distorting the region of interest chosen. A very long thin region of interest will cause much of the output window (page) to be blank.
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.
-rofi startx endx starty endy region of interest in terms of first and last pixels to use from the input data. If no region is selected it will use the whole of the region of interest used by ht.
-in file name of input file from edge detector. If not specified it will be read from the output file of ht. Relying on this, however, can be dangerous as ht may not know the full path to the edge data file and a different file with the same name could be picked up.
-o file name of output file. If not specified, output will go to a separate Xwindow with title the name of the ht file used. If an output file is specified, a postscript file will be generated.
-b option switch to mark the edge pixels which are associated with line segments in ht. On the screen these pixels are marked with a different colour, and in postscript are marked by a box around the edge point. This option can only be run if you run ht with the -pt option set.
-h option to read gf files produces by edged and canny for backward compatibility.
P.Palmer@ee.surrey.ac.uk September 1994