idlastro / Miscellaneous (Non-Astronomy) Procedures: ONE_ARROW

[Source code]

NAME
ONE_ARROW
PURPOSE
Draws an arrow labeled with a single character on the current device
EXPLANATION
ONE_ARROW is called, for example, by ARROWS to create a
"weathervane" showing the N-E orientation of an image.
CALLING SEQUENCE
one_arrow, xcen, ycen, angle, label, CHARSIZE = , THICK = , COLOR = 
                ARROWSIZE=, FONT =  ]
INPUT PARAMETERS
xcen, ycen = starting point of arrow, floating point scalars,
             In device coordinates unless /DATA or /NORMAL set
angle      = angle of arrow in degrees counterclockwise from +X direction
label      = single-character label (may be blank)
OUTPUT PARAMETERS none
OPTIONAL INPUT PARAMETERS
ARROWSIZE  = 3-element vector defining appearance of arrow.
        For device coordinates the default is  [30.0, 9.0, 35.0], 
        meaning arrow is 30 pixels long; arrowhead lines 9 pixels 
        long and inclined 35 degrees from arrow shaft.     For 
        normalized coordinates the default is divided by 512., for 
        data coordinates the default is multiplied by 
        (!X.crange[1] - !X.crange[0])/512..
CHARSIZE   = usual IDL meaning, default = 2.0
COLOR      = name or number give the color to draw the arrow.  See
      cgCOLOR for a list of color names.
/DATA - If set, then the input position (xcen, ycen) and the ARROWSIZE
         lengths are interpreted as being in data coordinates
FONT - IDL vector font number to use (1-20).   For example, to write
        the 'N' and 'E' characters in complex script, set font=13
/NORMAL - If set, then the input position (xcen, ycen) and the ARROWSIZE
         lengths are interpreted as being in normal coordinates
THICK      = usual IDL meaning, default = 2.0
EXAMPLE
Draw an triple size arrow emanating from the point (212,224)
and labeled with the character 'S'
IDL> one_arrow,212,224,270,'S',charsize=3
PROCEDURE
Calls one_ray to vector-draw arrow.
MODIFICATION HISTORY
Written by R. S. Hill, Hughes STX Corp., 20-May-1992.
Added font keyword, W.B. Landsman Hughes STX Corp. April 1995
Modified to work correctly for COLOR=0  J.Wm.Parker, HITC   1995 May 25
Add /NORMAL and /DATA keywords  W.Landsman    November 2006
Work with Coyote graphics W. Landsman  February 2011