legend.pro

basic median filter simulation

;+
; NAME:
;       LEGEND
; PURPOSE:
;       Create an annotation legend for a plot.
; EXPLANATION:
;       This procedure makes a legend for a plot.  The legend can contain
;       a mixture of symbols, linestyles, Hershey characters (vectorfont),
;       and filled polygons (usersym).  A test procedure, legendtest.pro,
;       shows legend's capabilities.  Placement of the legend is controlled
;       with keywords like /right, /top, and /center or by using a position
;       keyword for exact placement (position=[x,y]) or via mouse (/position).
; CALLING SEQUENCE:
;       LEGEND [,items][,keyword options]
; EXAMPLES:
;       The call:
;               legend,['Plus sign','Asterisk','Period'],psym=[1,2,3]
;         produces:
;               -----------------
;               |               |
;               |  + Plus sign  |
;               |  * Asterisk   |
;               |  . Period     |
;               |               |
;               -----------------
;         Each symbol is drawn with a plots command, so they look OK.
;         Other examples are given in optional output keywords.
;
;       lines = indgen(6)                       ; for line styles
;       items = 'linestyle '+strtrim(lines,2)   ; annotations
;       legend,items,linestyle=lines            ; vertical legend---upper left
;       items = ['Plus sign','Asterisk','Period']
;       sym = [1,2,3]
;       legend,items,psym=sym                   ; ditto except using symbols
;       legend,items,psym=sym,/horizontal       ; horizontal format
;       legend,items,psym=sym,box=0             ; sans border
;       legend,items,psym=sym,delimiter='='     ; embed '=' betw psym & text
;       legend,items,psym=sym,margin=2          ; 2-character margin
;       legend,items,psym=sym,position=[x,y]    ; upper left in data coords
;       legend,items,psym=sym,pos=[x,y],/norm   ; upper left in normal coords
;       legend,items,psym=sym,pos=[x,y],/device ; upper left in device coords
;       legend,items,psym=sym,/position         ; interactive position
;       legend,items,psym=sym,/right            ; at upper right
;       legend,items,psym=sym,/bottom           ; at lower left
;       legend,items,psym=sym,/center           ; approximately near center
;       legend,items,psym=sym,number=2          ; plot two symbols, not one
;       legend,items,/fill,psym=[8,8,8],colors=[10,20,30]; 3 filled squares
; INPUTS:
;       items = text for the items in the legend, a string array.
;               For example, items = ['diamond','asterisk','square'].
;               You can omit items if you don't want any text labels.
; OPTIONAL INPUT KEYWORDS:
;
;       linestyle = array of linestyle numbers  If linestyle[i] < 0, then omit
;               ith symbol or line to allow a multi-line entry.     If 
;               linestyle = -99 then text will be left-justified.  
;       psym = array of plot symbol numbers.  If psym[i] is negative, then a
;               line connects pts for ith item.  If psym[i] = 8, then the
;               procedure usersym is called with vertices define in the
;               keyword usersym.   If psym[i] = 88, then use the previously
;               defined user symbol
;       vectorfont = vector-drawn characters for the sym/line column, e.g.,
;               ['!9B!3','!9C!3','!9D!3'] produces an open square, a checkmark,
;               and a partial derivative, which might have accompanying items
;               ['BOX','CHECK','PARTIAL DERIVATIVE'].
;               There is no check that !p.font is set properly, e.g., -1 for
;               X and 0 for PostScript.  This can produce an error, e.g., use
;               !20 with PostScript and !p.font=0, but allows use of Hershey
;               *AND* PostScript fonts together.
;       N. B.: Choose any of linestyle, psym, and/or vectorfont.  If none is
;               present, only the text is output.  If more than one
;               is present, all need the same number of elements, and normal
;               plot behaviour occurs.
;               By default, if psym is positive, you get one point so there is
;               no connecting line.  If vectorfont[i] = '',
;               then plots is called to make a symbol or a line, but if
;               vectorfont[i] is a non-null string, then xyouts is called.
;       /help = flag to print header
;       /horizontal = flag to make the legend horizontal
;       /vertical = flag to make the legend vertical (D=vertical)
;       box = flag to include/omit box around the legend (D=include)
;		  outline_color = color of box outline (D = !P.color)
;       clear = flag to clear the box area before drawing the legend
;       delimiter = embedded character(s) between symbol and text (D=none)
;       colors = array of colors for plot symbols/lines (D=!P.color)
;       font = scalar font graphics keyword (-1,0 or 1) for text
;       textcolors = array of colors for text (D=!P.color)
;       margin = margin around text measured in characters and lines
;       spacing = line spacing (D=bit more than character height)
;       pspacing = psym spacing (D=3 characters) (when number of symbols is
;             greater than 1)
;       charsize = just like !p.charsize for plot labels
;       charthick = just like !p.charthick for plot labels
;       thick = array of line thickness numbers (D = !P.thick), if used, then 
;               linestyle must also be specified
;       position = data coordinates of the /top (D) /left (D) of the legend
;       normal = use normal coordinates for position, not data
;       device = use device coordinates for position, not data
;       number = number of plot symbols to plot or length of line (D=1)
;       usersym = 2-D array of vertices, cf. usersym in IDL manual. 
;             (/USERSYM =square, default is to use existing USERSYM definition)
;       /fill = flag to fill the usersym
;       /left_legend = flag to place legend snug against left side of plot
;                 window (D)
;       /right_legend = flag to place legend snug against right side of plot
;               window.    If /right,pos=[x,y], then x is position of RHS and
;               text runs right-to-left.
;       /top_legend = flag to place legend snug against top of plot window (D)
;       /bottom = flag to place legend snug against bottom of plot window
;               /top,pos=[x,y] and /bottom,pos=[x,y] produce same positions.
;
;       If LINESTYLE, PSYM, VECTORFONT, THICK, COLORS, or TEXTCOLORS are
;       supplied as scalars, then the scalar value is set for every line or
;       symbol in the legend.
; Outputs:
;       legend to current plot device
; OPTIONAL OUTPUT KEYWORDS:
;       corners = 4-element array, like !p.position, of the normalized
;         coords for the box (even if box=0): [llx,lly,urx,ury].
;         Useful for multi-column or multi-line legends, for example,
;         to make a 2-column legend, you might do the following:
;           c1_items = ['diamond','asterisk','square']
;           c1_psym = [4,2,6]
;           c2_items = ['solid','dashed','dotted']
;           c2_line = [0,2,1]
;           legend,c1_items,psym=c1_psym,corners=c1,box=0
;           legend,c2_items,line=c2_line,corners=c2,box=0,pos=[c1[2],c1[3]]
;           c = [c1[0]<c2[0],c1[1]<c2[1],c1[2]>c2[2],c1[3]>c2[3]]
;           plots,[c[0],c[0],c[2],c[2],c[0]],[c[1],c[3],c[3],c[1],c[1]],/norm
;         Useful also to place the legend.  Here's an automatic way to place
;         the legend in the lower right corner.  The difficulty is that the
;         legend's width is unknown until it is plotted.  In this example,
;         the legend is plotted twice: the first time in the upper left, the
;         second time in the lower right.
;           legend,['1','22','333','4444'],linestyle=indgen(4),corners=corners
;                       ; BOGUS LEGEND---FIRST TIME TO REPORT CORNERS
;           xydims = [corners[2]-corners[0],corners[3]-corners[1]]
;                       ; SAVE WIDTH AND HEIGHT
;           chdim=[!d.x_ch_size/float(!d.x_size),!d.y_ch_size/float(!d.y_size)]
;                       ; DIMENSIONS OF ONE CHARACTER IN NORMALIZED COORDS
;           pos = [!x.window[1]-chdim[0]-xydims[0] $
;                       ,!y.window[0]+chdim[1]+xydims[1]]
;                       ; CALCULATE POSITION FOR LOWER RIGHT
;           plot,findgen(10)    ; SIMPLE PLOT; YOU DO WHATEVER YOU WANT HERE.
;           legend,['1','22','333','4444'],linestyle=indgen(4),pos=pos
;                       ; REDO THE LEGEND IN LOWER RIGHT CORNER
;         You can modify the pos calculation to place the legend where you
;         want.  For example to place it in the upper right:
;           pos = [!x.window[1]-chdim[0]-xydims[0],!y.window[1]-xydims[1]]
; Common blocks:
;       none
; Procedure:
;       If keyword help is set, call doc_library to print header.
;       See notes in the code.  Much of the code deals with placement of the
;       legend.  The main problem with placement is not being
;       able to sense the length of a string before it is output.  Some crude
;       approximations are used for centering.
; Restrictions:
;       Here are some things that aren't implemented.
;       - An orientation keyword would allow lines at angles in the legend.
;       - An array of usersyms would be nice---simple change.
;       - An order option to interchange symbols and text might be nice.
;       - Somebody might like double boxes, e.g., with box = 2.
;       - Another feature might be a continuous bar with ticks and text.
;       - There are no guards to avoid writing outside the plot area.
;       - There is no provision for multi-line text, e.g., '1st line!c2nd line'
;         Sensing !c would be easy, but !c isn't implemented for PostScript.
;         A better way might be to simply output the 2nd line as another item
;         but without any accompanying symbol or linestyle.  A flag to omit
;         the symbol and linestyle is linestyle[i] = -1.
;       - There is no ability to make a title line containing any of titles
;         for the legend, for the symbols, or for the text.
; Side Effects:
; Modification history:
;       write, 24-25 Aug 92, F K Knight ([e-mail])
;       allow omission of items or omission of both psym and linestyle, add
;         corners keyword to facilitate multi-column legends, improve place-
;         ment of symbols and text, add guards for unequal size, 26 Aug 92, FKK
;       add linestyle(i)=-1 to suppress a single symbol/line, 27 Aug 92, FKK
;       add keyword vectorfont to allow characters in the sym/line column,
;         28 Aug 92, FKK
;       add /top, /bottom, /left, /right keywords for automatic placement at
;         the four corners of the plot window.  The /right keyword forces
;         right-to-left printing of menu. 18 Jun 93, FKK
;       change default position to data coords and add normal, data, and
;         device keywords, 17 Jan 94, FKK
;       add /center keyword for positioning, but it is not precise because
;         text string lengths cannot be known in advance, 17 Jan 94, FKK
;       add interactive positioning with /position keyword, 17 Jan 94, FKK
;       allow a legend with just text, no plotting symbols.  This helps in
;         simply describing a plot or writing assumptions done, 4 Feb 94, FKK
;       added thick, symsize, and clear keyword Feb 96, W. Landsman HSTX
;               David Seed, HR Wallingford, [e-mail]
;       allow scalar specification of keywords, Mar 96, W. Landsman HSTX
;       added charthick keyword, June 96, W. Landsman HSTX
;       Made keyword names  left,right,top,bottom,center longer,
;                                 Aug 16, 2000, Kim Tolbert
;       Added ability to have regular text lines in addition to plot legend 
;       lines in legend.  If linestyle is -99 that item is left-justified.
;       Previously, only option for no sym/line was linestyle=-1, but then text
;       was lined up after sym/line column.    10 Oct 2000, Kim Tolbert
;       Make default value of thick = !P.thick  W. Landsman  Jan. 2001
;       Don't overwrite existing USERSYM definition  W. Landsman Mar. 2002
;	     Added outline_color BT 24 MAY 2004
;       Pass font keyword to xyouts commands.  M. Fitzgerald, Sep. 2005
;       Default spacing, pspacing should be relative to charsize. M. Perrin, July 2007
;       Don't modify position keyword  A. Kimball/ W. Landsman Jul 2007
;       Small update to Jul 2007 for /NORMAL coords.  W. Landsman Aug 2007
;-
pro legend, items, BOTTOM_LEGEND=bottom, BOX = box, CENTER_LEGEND=center, $
    CHARTHICK=charthick, CHARSIZE = charsize, CLEAR = clear, COLORS = colorsi, $
    CORNERS = corners, DATA=data, DELIMITER=delimiter, DEVICE=device, $
    FILL=fill, HELP = help, HORIZONTAL=horizontal,LEFT_LEGEND=left, $
    LINESTYLE=linestylei, MARGIN=margin, NORMAL=normal, NUMBER=number, $
    POSITION=position,PSPACING=pspacing, PSYM=psymi, RIGHT_LEGEND=right, $
    SPACING=spacing, SYMSIZE=symsize, TEXTCOLORS=textcolorsi, THICK=thicki, $
    TOP_LEGEND=top, USERSYM=usersym,  VECTORFONT=vectorfonti, VERTICAL=vertical, $
    OUTLINE_COLOR = outline_color, FONT = font
;
;       =====>> HELP
;
compile_opt idl2
on_error,2
if keyword_set(help) then begin & doc_library,'legend' & return & endif
;
;       =====>> SET DEFAULTS FOR SYMBOLS, LINESTYLES, AND ITEMS.
;
 ni = n_elements(items)
 np = n_elements(psymi)
 nl = n_elements(linestylei)
 nth = n_elements(thicki)
 nv = n_elements(vectorfonti)
 nlpv = max([np,nl,nv])
 n = max([ni,np,nl,nv])                                  ; NUMBER OF ENTRIES
strn = strtrim(n,2)                                     ; FOR ERROR MESSAGES
if n eq 0 then message,'No inputs!  For help, type legend,/help.'
if ni eq 0 then begin