IRAF help page for package lists, program rgcursor

gcursor

Task rgcursor iteratively reads the graphics cursor, writing the cursor values to the standard output. The standard output is normally redirected into a text file to generate a coordinate list to be used as input to one or more other programs. Any IRAF program which reads the graphics cursor may be run taking input from a list prepared in advance with rgcursor (as well as interactively, of course).

A plot should be drawn on the graphics terminal before running rgcursor. When the program is run a loop is entered, reading the global graphics cursor until the end of file character (e.g., , ) is typed. Each cursor read causes a line to be printed on the standard output, after which the cursor is again read.

While the program is waiting for the cursor to be read, i.e., whenever the cursor crosshairs are displayed, the terminal is said to be in "cursor mode". While in cursor mode, various commands may be entered, e.g., to zoom in a feature to get a more accurate cursor position, without terminating the current cursor read. To read the cursor position, enter any key not recognized as a cursor mode command, i.e., any lower case or nonalphanumeric character. The actual character one should type depends upon the program for which the list is intended. If the program will use only the X and Y coordinates of the cursor any character may be typed, e.g., tap the space bar. If the program uses the key to determine what action to take, then you must type a specific key.

The X and Y coordinates of the cursor position and other information comprising the cursor value are printed on the standard output when the cursor is read. The cursor position may optionally be marked whenever the cursor is read, by setting the ":.markcur" option when in cursor mode. This is useful when preparing long lists to keep track of the objects or features that have already been marked.

For additional information on cursor mode and the format of a cursor value string, type "help cursor". For information on the key and string values required by the applications program for which the cursor list is intended, consult the documentation for that program.

1. Interactively generate a starlist (file "starlist") to be used as input to another program, e.g., for digital photometry. In this case one would probably want to start with a contour plot labeled in image pixel coordinates.

	cl> contour m74			# make the plot
	cl> rgcursor > starlist		# make the object list
	At this point, the cursor loop is entered and the terminal
	is placed into cursor mode.  Any of the following commands
	might be appropriate:
	command		action
	:.markcur+	enables marking of the cursor position
			    when the cursor is read
	:radius 7	set object radius in pixels
	:annulus 10 15	set annulus radii to be used for sky
	space_bar	mark the position of an object
	space_bar	mark the position of an object
				(etc.)
	
	Z		zoom in on a feature to get a more
			    accurate cursor read
	space_bar	mark the position of the object
	space_bar	mark the position of another object
	0		replot the original plot
	
		(EOF) terminates rgcursor

Given the above command sequence, the output file "starlist" might contain the following cursor values.

	234.435 78.9292 1 : radius 7
	234.475 78.9243 1 : annulus 10 15
	67.2822 282.319 1 
	766.252 344.224 1 
	822.918 311.748 1 
	76.8272 822.139 1