pro tvellipse, rmax, rmin, xc, yc, pos_ang, color, DATA = data, $ NPOINTS = npoints, COLOR=thecolor, MAJOR=major, MINOR=minor, $ _Extra = _extra ;+ ; NAME: ; TVELLIPSE ; ; PURPOSE: ; Draw an ellipse on the current graphics device. ; ; CALLING SEQUENCE: ; TVELLIPSE, rmax, rmin, xc, yc, [ pos_ang, color, COLOR= ,/DATA, NPOINTS= ; LINESTYLE=, THICK=, /MAJOR, /MINOR ] ; INPUTS: ; RMAX,RMIN - Scalars giving the semi-major and semi-minor axes of ; the ellipse ; OPTIONAL INPUTS: ; XC,YC - Scalars giving the position on the TV of the ellipse center ; If not supplied (or if XC, YC are negative and /DATA is not set), ; and an interactive graphics device (e.g. not postscript) is set, ; then the user will be prompted for X,Y ; POS_ANG - Position angle of the major axis, measured counter-clockwise ; from the X axis. Default is 0. ; COLOR - Scalar giving intensity level to draw ellipse. The color ; can be specified either with either this parameter or with the ; COLOR keyword. Default is !P.COLOR ; ; OPTIONAL KEYWORD INPUT: ; COLOR - Intensity value used to draw the circle, overrides parameter ; value. Default = !P.COLOR ; /DATA - if this keyword is set and non-zero, then the ellipse radii and ; X,Y position center are interpreted as being in DATA ; coordinates. Note that the data coordinates must have been ; previously defined (with a PLOT or CONTOUR call). ; NPOINTS - Number of points to connect to draw ellipse, default = 120 ; Increase this value to improve smoothness ; /MAJOR - Plot a line along the ellipse's major axis ; /MINOR - Plot a line along the ellipse's minor axis ; ; Any keyword recognized by PLOTS is also recognized by TVELLIPSE. ; In particular, the color, linestyle, thickness and clipping of ; the ellipses are controlled by the COLOR, LINESTYLE, THICK and ; NOCLIP keywords. (Clipping is turned off by default, set ; NOCLIP=0 to activate it.) ; ; RESTRICTIONS: ; TVELLIPSE does not check whether the ellipse is within the boundaries ; of the window. ; ; The ellipse is evaluated at NPOINTS (default = 120) points and ; connected by straight lines, rather than using the more sophisticated ; algorithm used by TVCIRCLE ; ; TVELLIPSE does not accept normalized coordinates. ; ; TVELLIPSE is not vectorized; it only draws one ellipse at a time ; ; EXAMPLE: ; Draw an ellipse of semi-major axis 50 pixels, minor axis 30 ; pixels, centered on (250,100), with the major axis inclined 25 ; degrees counter-clockwise from the X axis. Use a double thickness ; line and device coordinates (default) ; ; IDL> tvellipse,50,30,250,100,25,thick=2 ; ; NOTES: ; Note that the position angle for TVELLIPSE (counter-clockwise from ; the X axis) differs from the astronomical position angle ; (counter-clockwise from the Y axis). ; ; REVISION HISTORY: ; Written W. Landsman STX July, 1989 ; Converted to use with a workstation. M. Greason, STX, June 1990 ; LINESTYLE keyword, evaluate at 120 points, W. Landsman HSTX Nov 1995 ; Added NPOINTS keyword, fixed /DATA keyword W. Landsman HSTX Jan 1996 ; Check for reversed /DATA coordinates P. Mangiafico, W.Landsman May 1996 ; Converted to IDL V5.0 W. Landsman September 1997 ; Work correctly when X & Y data scales are unequal December 1998 ; Removed cursor input when -ve coords are entered with /data ; keyword set P. Maxted, Keele, 2002 ; Use _EXTRA keywords including NOCLIP W. Landsman October 2006 ; Add plotting of major and minor axes and /MAJOR, /MINOR keywords; ; fixed description of RMAX,RMIN (semi-axes). J. Guerber Feb. 2007 ;- On_error,2 ;Return to caller if N_params() lt 2 then begin print,'Syntax - TVELLIPSE, rmax, rmin, xc, yc, [pos_ang, color, COLOR=,' print,' NPOINTS=, LINESTYLE=, THICK=, /DATA, /MAJOR, /MINOR ]' print,' any other keywords accepted by PLOTS' return endif if N_params() lt 4 then $ cursor, xc, yc, /DEVICE, /NOWAIT ;Get unroamed,unzoomed coordinates if ( (xc LT 0) or (yc LT 0)) and not(keyword_set(data)) then begin message,'Position cursor in window ' + strtrim(!D.WINDOW,2) + $ ' -- then hit mouse button',/INF cursor, xc, yc, /DEVICE, /WAIT message,'Ellipse is centered at (' + strtrim(xc,2) + ',' + $ strtrim(yc,2) + ')',/INF endif if N_params() LT 5 then pos_ang = 0. ;Default position angle if N_Elements(TheColor) EQ 0 then begin IF N_Elements( Color ) eq 0 THEN Color = !P.COLOR endif else color = TheColor if not keyword_set(NPOINTS) then npoints = 120 ;Number of points to connect phi = 2*!pi*(findgen(npoints)/(npoints-1)) ;Divide circle into Npoints ang = pos_ang/!RADEG ;Position angle in radians cosang = cos(ang) sinang = sin(ang) x = rmax*cos(phi) ;Parameterized equation of ellipse y = rmin*sin(phi) xprime = xc + x*cosang - y*sinang ;Rotate to desired position angle yprime = yc + x*sinang + y*cosang if keyword_set(data) then $ plots, xprime, yprime, /DATA, COLOR=color, _STRICT_Extra = _extra else $ plots, round(xprime), round(yprime), COLOR=color, /DEVICE, $ _STRICT_Extra = _extra if keyword_set(major) then begin xmaj = xc + [rmax,-rmax]*cosang ; rot & transl points (rmax,0),(-rmax,0) ymaj = yc + [rmax,-rmax]*sinang if keyword_set(data) then $ plots, xmaj, ymaj, /DATA, COLOR=color, _STRICT_Extra=_extra $ else plots, round(xmaj), round(ymaj), $ /DEVICE, COLOR=color, _STRICT_Extra=_extra endif if keyword_set(minor) then begin xmin = xc - [rmin,-rmin]*sinang ; rot & transl points (0,rmin),(0,-rmin) ymin = yc + [rmin,-rmin]*cosang if keyword_set(data) then $ plots, xmin, ymin, /DATA, COLOR=color, _STRICT_Extra=_extra $ else plots, round(xmin), round(ymin), $ /DEVICE, COLOR=color, _STRICT_Extra=_extra endif return end