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Re: TVIM display routine on 24-bit displays

David Williams <d.williams@qub.ac.uk> writes:

> Hi, there.
> I've recently made the switch (as a user, not as sysadmin!) from a Sun
> Ultra running Solaris to a PC running Red Hat 6.2. No big deal, perhaps,
> but I'm having to come to terms with using a decent graphics card with
> 24-bit colour when using IDL (and the various astronomy add-ons like CDS
> and SolarSoft).
> My problem is this: I used to use a very nifty display routine by Paul
> Ricchiazzi called TVIM.PRO, which always did the job brilliantly for me.
> It still plots fine on a postscript device, but when you use it to
> display an image on your 24-bit colour XWindow, the colour table doesn't
> scale nicely. If you're using colour table 0 (greyscale), for example,
> to view a 2-D image, then it doesn't scale from black (minimum data
> value) to white (maximum data value) as it would under an 8-bit display.
> I know that the colour system under 24-bit isn't as straightforward as
> under 8-bit, for which (I read) IDL is optimised.
> Because so many of my routines (and some of my colleagues') depend on
> TVIM and all its nice keywords, does anyone know of a way to make TVIM
> display things properly on a 24-bit XWindow? The only kludge I've been
> able to get to work so far has been to get our sysadmin to cripple the
> machine's display to 8-bit colour, which seems like a rather ham-fisted
> way of doing things.
> Any help would be _greatly_ appreciated,
> thanks for taking the time to read this,
> Dave Williams,
> Belfast.

Hi Dave,

You're in luck.  I recently put 24-bit color into tvim.  This new
version is included in an updated version of the esrg idl library,
available from:


and to make things easy I've also included it below.


Paul Ricchiazzi


; ROUTINE:  tvim
; USEAGE:   tvim,a
;           tvim,a,scale=scale,range=range,xrange=xrange,yrange=yrange,     $
;                aspect=aspect,title=title,xtitle=xtitle,ytitle=ytitle,     $
;                noaxis=noaxis,interp=interp,colors=colors,c_map=c_map,     $
;                stitle=stitle,rmarg=rmarg,clip=clip,labels=labels,         $
;                pcharsize=pcharsize,lcharsize=lcharsize,nbotclr=nbotclr,   $
;                clevels=clevels,nodata=nodata,rgb_nodata=rgb_nodata,       $
;                barwidth=barwidth,position=position,noframe=noframe,rct=rct
; PURPOSE:  Display an image with provisions for
;            1. numbered color scale 
;            2. plot title
;            3. annotated x and y axis 
;            4. simplified OPLOT capability
;            5. manual or automatic scaling with smooth or discreet colors
;            6. special treatment of "invalid data" pixels
;            7. display true color images
; INPUT    
;   a           image quantity
;               if A is a two dimensional array it is assumed to be an
;               array of a physical quantity in the same units as specified
;               in RANGE.  
;               if A is a three dimensional array it is assumed to be a 
;               band-interleaved true color image in the form
;               (3,nx,ny) or (nx,ny,3) [either form will work], where 
;               nx and ny are the number of pixels in the x and y
;               directions and the red, green and blue components are
;               specified by the third index.  All keywords associated
;               with scaling the image to the color key (e.g., SCALE,
;               RANGE, CLEVELS, STITLE etc.) are disabled for true color
;               images.
;               Before display the image array is scaled to the 0-255
;               range using bytscl.  It is then routed through the
;               color tables. The red color table array contains the
;               intensity translation table for the red image, and so
;               forth. Assuming that the color tables have been loaded
;               with the vectors R, G, and B, a pixel with a color
;               value of (r, g, b) is displayed with a color of (R[r],
;               G[g], B[b]). As with other devices, a color table
;               value of 255 represents maximum intensity, while 0
;               indicates an absence of the color. To pass the RGB
;               pixel values without change, load the red, green and
;               blue color tables with a ramp with a slope of 1.0:
;               TVLCT, INDGEN(256), INDGEN(256), INDGEN(256) or with
;               the LOADCT procedure: LOADCT, 0 ; Load standard
;               black/white table.
;               True color images can be written to postscript using
;                    toggle,/color
;                    tvim,a
;                    toggle
;               NOTE: To write a gif image you'll have to use color_quan to 
;                     quantize the true color image into 256 colors. This
;                     procedure produces a pretty lousy result:
;                     v=color_quan(a,3,r,g,b,color=256)
;                     tvlct,r,g,b
;                     tvim,v
;                     gif_write,'junk.gif'
;               NOTE: if you have a pc you can use a screen capture 
;                     to cut and paste the image into a document ("ALT
;                     print-screen" copies the screen into the paste
;                     buffer).
; Optional keyword input:
;  title
;    plot title
;  xtitle
;    x axis title
;  ytitle
;    y axis title
;  stitle
;    color key title (drawn to the right of color scale)
;  rmarg 
;    right margin expansion factor to provide more room for extra wide
;    color scale annotation (default=1)
;  xrange
;    array spanning entire x axis range. (default = [0,x_dimension-1])
;  yrange
;    array spanning entire y axis range. (default = [0,y_dimension-1])
;    NOTE:TVIM only uses min(XRANGE), max(XRANGE), min(YRANGE) and max(YRANGE).
;  scale
;    if set draw color scale.  SCALE=2 causes steped color scale
;  range
;    two or three element vector indicating physical range over which
;    to map the color scale.  The third element of RANGE, if specified, 
;    sets the step interval of the displayed color scale.  It has no
;    effect when SCALE is not set. E.g., RANGE=[0., 1., 0.1] will
;    cause the entire color scale to be mapped between the physical
;    values of zero and one; the step size of the displayed color
;    scale will be set to 0.1.
;  clip
;    specifies a set percentage of pixels which will be left outside
;    the color scale.  Larger values of CLIP yield images with greater
;    contrast. For example if clip=2 then the color scale range will
;    be set to include 98% of the pixels and to exclude the brightest
;    1% and the dimmest 1% of the pixel brightness distribution.
;    Keyword RANGE overides the effect of CLIP.
;    If CLIP is a two element vector, the upper and lower percentile
;    range can be specified.  For example CLIP=[0,95] will exclude the
;    top 5%.  
;    An alternative is to set CLIP to a single negative integer.  This
;    causes the grey scale range to be obtained from the max and min
;    value of the image array after it is filtered by a 2-D median
;    filter. The radius of the median filter is set to -clip.  Median
;    filtering is effective in removing "salt and pepper" noise,
;    (isolated high or low values). For example, setting clip=-1
;    causes the code to check the 9 element superpixel centered at
;    each pixel for median values.  A single extremely large or small
;    value does not affect the final value of the median at each pixel
;    point.
;  aspect
;    the x over y aspect ratio of the output image. If not set, aspect
;    is set to (size_x/size_y) of the input image.
;  position
;    specifies the lower left and upper right TVIM frame position in
;    normal coordinates.  When set POSITION overides the setting of
;    ASPECT, and disables screen blanking for new plots.
;  noaxis
;    if set do not draw x and y numbered axis around image. Instead
;    just draw a box
;  noframe
;    if set no not draw anything around image, not even a box
;  interp
;    TVIM normally uses nearest neighbor sampling to resize the image
;    to fill the data window area. If INTERP is set the resizing
;    operation uses bilinear interpolation
;    If INTERP = 2 the interpolation range is adjusted so that there
;    is a half pixel border around the plot.  This ensures that the
;    smoothed image properly represents the cell center values of the
;    pixels, but introduces an extrapolation on the outer edges.  This
;    option has noticeable effects for small (<20) image arrays.
;    NOTE: When writing to a Postscript file the resizing operation is
;    accomplished by changing the pixel size.  Thus the INTERP
;    parameter has no effect on Postscript output.
;  pcharsize
;    character size of numbers along x and y axis and the title
;    (default is !p.charsize if non-zero, 1 otherwise)
;    NOTE: The character size of the x and y-axis number scale
;    annotation may be independently controlled by the !x.charsize or
;    !y.charsize system variables.  For example, the x and y axis
;    number scale characters may be made invisible by setting these
;    variables to a very small non-zero number before calling TVIM.
;    Remember to restore normal character sizes by setting !x.charsize
;    and !y.charsize to 1 or zero after the call to TVIM.
;  lcharsize
;    character size of color key number or labels (default is
;    !p.charsize if non-zero, 1 otherwise)
;  barwidth
;     width of color key which appears to right of image when SCALE is
;     set.  (default=1)
;  labels
;     a vector of strings used to label the color key levels.  If not
;     set the default color key number labels are used.  If the number
;     of elements in LABELS is the same as the number of elements in
;     COLORS then the labels will appear in the middle of a given
;     color band instead of at the boundary between colors.  If COLORS
;     is not set the number of elements in LABELS should be at least
;     as large as the number of color key segments plus one.
;  colors
;     an array of color indicies.  When the COLORS array is set TVIM
;     will map values of A into the color values specified in COLORS.
;     How physical values are assigned to color values depends on how
;     the RANGE parameter is set, as shown in this table:
;             RANGE           color_value
;             -----           -----------
;       1.  not set          COLORS(A)
;       2.  [amin,amax]      COLORS((A-amin)/dinc)
;       3.  [amin,amax,inc]  COLORS((A-amin)/inc)
;     where amin, amax and inc are user specified elements of RANGE
;     and dinc=(amax-amin)/n_elements(COLORS).  In case 1, A is used
;     directly as a subscript into COLORS.  When RANGE is not set
;     legend labels should be used to annotate the color values. In
;     case 2, A is scaled so that each color defined in COLORS
;     represents a proportionate fraction of the total dynamic range.
;     In case 3, amin and inc (and not amax) are used to control which
;     colors are associated with given physical values.  See examples.
;  c_map
;     TVIM normally rescales the input image to span the entire color
;     table range. Setting C_MAP disables this automatic re-scaling.
;     This is useful when the image byte values correspond to a
;     particular color mapping that could be destroyed by the
;     rescaling process (E.G.  a gif image).
;     NOTE: When the number of IDL color table entries is less than
;     256 some colors may be lost. Use a private color map to avoid
;     this. See examples.
;  nbotclr
;     number of reserved colors at the bottom of the color
;     table.  Color values between 0 and nbotclr-1 will not
;     be used in the displayed image.  This allows the
;     bottom of the table to be set to special colors which
;     will not be used in the displayed the image.  This
;     keyword is disabled when either the COLORS or NODATA 
;     options are used.  (default=1)
;     NOTE: by default the color table indicies used within a TVIM
;     image is limited to the range 1 to !d.n_colors-2. In most
;     predefined color tables, color index 0 and !d.n_color-1
;     correspond to pure black and white, respectively. TVIM uses
;     these color indicies as background and foreground colors for
;     region blanking and axis annotation. Color tables which do not
;     define black and white in these index locatations are not good
;     choices for TVIM plots, unless the first and last color table
;     entries are redefined as black and white using TVLCT, e.g.,
;     tvlct,0,0,0,0 & tvlct,255,255,255,!d.n_colors-1
;     NOTE: the procedure DCOLORS can be used to load a set
;     of discreet colors in the bottom 11 color values
;     (0-10). The original color table is resampled to fit
;     between color value 11 and the !d.n_colors-1.
;  nodata
;     pixel values which are interpreted as invalid data.  Pixels
;     containing this data value are colored with color RGB_NODATA.
;  rgb_nodata
;     an RGB value (a 3 component vector) used to color pixels filled
;     with invalid data. (default = [0,0,0])
;     NOTE: NODATA and RGB_NODATA override the effect of NBOTCLR
;  rct
;     if set, reverse direction of color table.  This keyword can be
;     used on black & white printers to allow large field values to be
;     represented by dark colors.  Note, this feature is implemented
;     by reversing the association between physical values and color.
;     Though it reverses the colors on the color key, it does not
;     affect the actual color table.
;   clevels 
;     physical values at the color key tic marks.  Use this to set
;     contour levels in a subsequent call to CONTOUR.
;     Setting SCALE=2 changes the color scale using the STEP_CT
;     procedure.  The color scale may be returned to its original
;     state by the command, STEP_CT,/OFF
;     TVIM first determines the size of the plot data window with a
;     dummy call to PLOT.  When the output device is "X", CONGRID is
;     used to scale the image to the size of the available data
;     window.  Otherwise, if the output device is Postscript,
;     scaleable pixels are used in the call to TV.
;     If the input image quantity is not of type byte, TVIM converts
;     them to byte by scaleing the input between 0 and !d.n_colors-1.
;     If the input is already a byte array and if either the number of
;     color table entries is 256 or if C_MAP is set, then no scaling
;     is done.  This is to ensure consistency with specially defined
;     private color tables.
;     After the the image is drawn TVIM calls PLOT again to draw the x
;     and y axis and titles.  Finally if scale is set, TVIM calls the
;     COLOR_KEY procedure to draw the color scale just to the right of
;     the data window.
;     A stepped color scale (SCALE = 2 option) is not available when
;     writing to a black & white postscript file (i.e., when the
;     DEVICE color option is not enabled).
;;;    Plot a GIF image with its own preset RGB
;;;    table (perhaps from a digitized video image)
; window,colors=256            ; set up a private color map
; read_gif,'/home/paul/gif/el-nino.gif',im,r,g,b
; tvlct,r,g,b
; tvim,im,/c_map
;;;    Plot an image with descreet greyscale values to a printer
;;;    which has its own hard-wired color table. check documentation of gray.pro
; im=randata(128,128,s=4)
; immx=max(im) & immn=min(im)
; !p.multi=[0,2,2]
; loadct,5
; tvim,im,/scale,range=[immn,immx],color=gray(4)
; tvim,im,/scale,range=[immn,immx],color=gray(5)
; tvim,im,/scale,range=[immn,immx],color=gray(8)
; tvim,im,/scale,range=[immn,immx],color=gray(10)
;;;    Display a map of surface types (green=veg, blue=water, red=sand)
;;;    Notice how RANGE is used to associate physical values with colors.
;;;    (use im from the previous example)
; im=randata(128,128,s=4)
; immx=max(im) & immn=min(im) & delim=immx-immn
; tvlct,[0,0,0,255],[0,255,0,0],[0,0,255,0]
; !p.multi=[0,2,2]
; colors=[1,2,3] & labels=[' veg',' water',' sand']
; range=[immn,immx,delim/3]
; tvim,im,/scale
; tvim,im,colors=colors,range=range,/scale
; tvim,im,colors=colors,range=range,/scale,labels=labels,lch=2
; !p.multi=0
; range=[immn-.25*delim,immx+.25*delim,delim/2]
; lbl=[' veg!c region 1',' water!c region 2',' sand!c region 3']
; tvim,im,colors=colors,range=range,/scale,labels=lbl,lch=2,rmarg=2,pchar=1.2
;;;   Display the image from previous example and overlay a contour plot
; !p.multi=0
; loadct,5
; im=randata(128,128,s=4)
; immx=max(im) & immn=min(im) & delim=immx-immn
; xrange=[-120,-100]
; yrange=[20,50]
; range=[immn,immx]
; xx=findrng(xrange,128)
; yy=findrng(yrange,128)
; tvim,im,/scale,xrange=xrange,yrange=yrange,clevels=clevels,range=range
; contour,im,xx,yy,levels=clevels,/overplot
;;;    NOTE: You might prefer the results obtained from procedure CONFILL.
; confill,im,xx,yy,/asp,levels=clevels
;;;    Display a grey scale image and annotate certain points in color
; loadct,0
; dcolors
; tvim,im,/scale,nbotclr=11                    ; reserve some colors at bottom
; xx=interpolate([40,80],randomu(iseed,10))
; yy=interpolate([40,80],randomu(iseed,10))
; plots,xx,yy,psym=2,color=1+indgen(10)
;;;   inset an image onto a line plot
;     !p.multi=0
;     loadct,0
;     xy=randata(100,100,s=3)
;     plot,xy[*,40]
;     tvim,xy,pos=boxpos(/cur),title='transect',pcharsize=.7
;     oplot,[0,99],[40,40]
;;;    Display a grey scale image and show nodata values in red
; loadct,0
; im=randata(100,100,s=4.5)
; im(randomu(iseed,50)*9999)=-999.
; tvim,im,/scale,nodata=-999.,rgb_nodata=[255,0,0]
;;;    Postscript output with a reversed color scale.  Because the
;;;    background color is always RGB=(255,255,255) you must set the
;;;    default color, !p.color, to a dark color if you want good contrast
;;;    between the axis labels and the white paper.   According to 
;;;    Didier's reversed color table a color index of 255 should produce
;;;    black, but for some reason !p.color=255 doesn't work right.
;;;    I think IDL is iterpreting !p.color=255 in some special way.
;;;    So instead use !p.color=254; this seems to work fine.
; toggle,/color
; loadct,28
; !p.color=254              ; don't use 255, don't ask me why
; tvim,dist(20),/scale
; toggle
;;; display data defined on a regular LAT-LON grid onto a given map 
;;; projection.  USE MAP_SET and MAP_IMAGE to create the map projection
;;; and to warp the image.  Then use BOXPOS to position the TVIM frame
;;; to correctly register the map and image
; w8x11
; IMAGE = sin(!pi*findrng(0,24,200))#sin(!pi*findrng(0,12,200))
; !p.multi=[0,1,2]
; map_set,45,0,/ortho,/advance,pos=boxpos(/aspect)
; newimage=map_image(image,/bilin,latmin=-90,latmax=90,lonmin=-180,lonmax=180)
; tvim,newimage,title='Warped data',pos=boxpos(/get),/scale
; map_set,45,0,/ortho,pos=boxpos(/get),/grid,/cont,/noerase ; draw map
; tvim,image,xrange=[-180,180],yrange=[-90,90],/scale, $
;     title='Unwarped data',xtitle='Longitude',ytitle='Latitude'
; map_set,0,0,/cyl,pos=boxpos(/get),/grid,/cont,/noerase ; draw map
;;; use MAP_SET2 to mask out land areas. Note that the example below is
;;; unusual.   MAP_SET2 doesn't always produce such nicely filled land areas.
;;; Typically one must run MAP_SET2 with /SAVE
;;; to create a ascii file containing the continental boundary lat-lon
;;; coordinates. Then use an editor  to group the continental coordinates 
;;; line segments to form closed contours which POLYFILL can understand 
;;; (the call to POLYFILL is enabled by setting con_color).
; image=randata(256,256,s=2.5)
; tvim,image,yrange=[-65.1,-64],xrange=[-64.5,-62]
; map_set5,-64,-64,/cont,limit=[-65.1,-64.5,-64,-62],/pos,/noerase
; map_set,-64,-64,/cont,limit=[-65.1,-64.5,-64,-62],pos=bospos(/get),/noerase
;;; display a true color image
; a=fltarr(100,100,3)
; g=bytscl(replicate(1,100)#(findgen(100)>30))
; a(*,*,0)=rotate(g,1)
; a(*,*,1)=g
; a(*,*,2)=rotate(g,3)
; !p.multi=[0,2,2]
; loadct,0
; tvim,a,xrange=[100,300],yrange=[0,10],title='true color image'
; tvim,a(*,*,0),range=[0,255],title='red component'
; tvim,a(*,*,1),range=[0,255],title='green component'
; tvim,a(*,*,2),range=[0,255],title='blue component'
;;; other interleaving possibility
; a=fltarr(3,100,100)
; g=bytscl(replicate(1,100)#(findgen(100)>30))
; a(0,*,*)=rotate(g,1)
; a(1,*,*)=g
; a(2,*,*)=rotate(g,3)
; !p.multi=[0,2,2]
; loadct,0
; tvim,a,xrange=[100,300],yrange=[0,10],title='true color image'
; tvim,a(0,*,*),range=[0,255],title='red component'
; tvim,a(1,*,*),range=[0,255],title='green component'
; tvim,a(2,*,*),range=[0,255],title='blue component'
;;; display a sparse data field superposed on a background topography.
;;; topography shown with a gray scale, data filled areas shown with
;;; color table 5
; minval=.1                   ; minimum physical value of interest
; nbotclr=30                  ; number of colors assigned to gray scale
; maxgray=240                 ; max gray scale intensity (240 out of 255)
; topo=randata(200,200,s=4)   ; background topography variable (just for looks)
; data=randata(200,200,s=2)   ; data variable
; loadct,5                    ; color table 5
; topo=topo-max(topo)
; rngdata=max(data)-minval
; rngtopo=-min(topo)
; topo=nbotclr/(!d.n_colors<256.-nbotclr)*rngdata*topo/rngtopo
; topo=topo+minval
; ii=where(data lt minval)
; data[ii]=topo[ii]
; r=findrng(0,maxgray,nbotclr) & g=r & b=r
; tvlct,r,g,b,0
; tvim,data,rmarg=1
; color_key,range=data>minval,nbotclr=nbotclr
; AUTHOR:       Paul Ricchiazzi    oct92 
;               Earth Space Research Group, UCSB
; 28jan93: switched from PUT_COLOR_SCALE to COLOR_KEY
; 11feb93: added INTERP keyword
; 11feb93: added C_MAP keyword
; 11feb93: added STITLE keyword
; 20apr93: added RMARG keyword, centered image in plot window
; 23apr93: call COLOR_KEY before TV. Now stepped color scales copy to PS file
; 10sep93: deal with perfectly flat images. No more math error when a=0
; 14sep93: added CLIP keyword
; 11feb94: added PCHARSIZE,LCHARSIZE,LABELS, and COLORS keywords
; 18feb94: added NBOTCLR keyword
; 16mar94: added INTERP=2 option and adjusted centering of pixels
; 08Jul94: added NODATA and RGB_NODATA keywords
; 04Aug94: added BARWIDTH keyword 
; 04Aug94: defaulted PCHARSIZE and LCHARSIZE to !P.CHARSIZE if non-zero
; 02Mar95: added POSITION keyword
; 31Mar95: added NOAXIS keyword
; 24may95: initial sizing includes allowance for PCHARSIZE > 1
; 06sep95: color indecies used in plot now run from 1 to !d.ncolors-2
; 24jul96: do a REFORM(a) to allow tvim,a(1,*,*) to work with no complaints
; 01sep96: added the RCT keyword
; 17may00; treat true color images
; 01dec00; when position keyword is set, add to current page 

pro tvim,a,scale=scale,range=range,xrange=xrange,yrange=yrange,$

if n_params() eq 0 then begin

if keyword_set(position) then begin

if keyword_set(pcharsize) eq 0 then begin
  if !p.charsize eq 0 then pcharsize=1 else pcharsize=!p.charsize

if keyword_set(lcharsize) eq 0 then begin
  if !p.multi(1)>!p.multi(2) gt 2 then lcharsize=.5*pcharsize $
                                  else lcharsize=pcharsize

if not keyword_set(interp) then interp=0


if sz(0) eq 3 then begin
  case 1 of 
    sz(1) eq 3: true_index=1
    sz(3) eq 3: true_index=3
    else: message,'true color array must be of form (nx,ny,3) or (3,nx,ny)'
  if true_index eq 1 then begin
  endif else begin
endif else begin

plot, [0,1],[0,1],/nodata,xstyle=4,ystyle=4,charsize=pcharsize

if keyword_set(scale) or keyword_set(rmarg) then begin
  if keyword_set(rmarg) eq 0 then begin
    if(!d.name eq "WIN") then begin
    endif else begin
  if keyword_set(stitle) then xmarg=xmarg+2*!d.y_ch_size*lcharsize
if keyword_set(aspect) eq 0 then aspect=float(nx)/ny
if xsize gt ysize*aspect then xsize=ysize*aspect else ysize=xsize/aspect 
if xsize lt oxs then px(0)=px(0)+.5*(oxs-xsize)
if ysize lt oys then py(0)=py(0)+.5*(oys-ysize)

if keyword_set(position) then begin


if true_color then begin  ; true color image

  if !d.name eq 'PS' then begin
  endif else begin
    if interp lt 2 then begin
    endif else begin
    if true_index eq 3 $
      then tv,interpolate(bytscl(a),fx,fy,indgen(3),/grid),px(0),py(0),true=3 $
      else tv,interpolate(bytscl(a),indgen(3),fx,fy,/grid),px(0),py(0),true=1 

endif else begin
  max_color=(!d.n_colors-2) < 255
  if keyword_set(title) eq 0 then title=''
  if n_elements(nodata) then begin
    if n_elements(rgb_nodata) eq 0 then rgb_nodata=[0,0,0]
    iinodata=where(a eq nodata,ncnd)
    iidata=where(a ne nodata,ncgd)
    if ncgd gt 0 then begin
  endif else begin
  if num_range eq 1 then message,'must specify either 2 or 3 elements of RANGE'
  if num_range eq 0 then begin
    if amin eq amax then begin
      case 1 of
        amax eq 0.: rng=[-1,1.]
        amax gt 0.: rng=[0,2*amax]
        amax lt 0.: rng=[2*amax,0]
    endif else BEGIN
      CASE n_elements(clip) OF
        1:if clip ge 0 then begin
        endif else begin
          ix1=-clip & ix2=nx+clip
          iy1=-clip & iy2=ny+clip
  endif else begin
    if num_range eq 3 then inc=range(2) else inc=0
  case 1 of
    ncolors ne 0 : begin
      if keyword_set(rct) then message,'rct invalid with color specificaton'
      case num_range of 
    keyword_set(c_map) eq 1 : begin
      if keyword_set(rct) then message,'rct invalid with c_map specificaton'
    else: begin
;    if keyword_set(nbotclr) eq 0 then nbotclr=0 else nbotclr=nbotclr
      if keyword_set(nbotclr) eq 0 then nbotclr=1 else nbotclr=nbotclr
      aa=nbotclr+max_color*((float(reform(a))-rng(0))/(rng(1)-rng(0)) >0.<1.)
      if keyword_set(rct) then aa=max_color+2*nbotclr-aa
  if keyword_set(scale) then begin
    if scale eq 2 then step=1 else step=0
    if not keyword_set(barwidth) then barwidth=1
    if ncolors eq 0 then begin
    endif else begin
  if iinodata(0) ne -1 then aa(iinodata)=1
  if !d.name eq 'PS' then begin
  endif else begin
    if interp lt 2 then begin
    endif else begin
if keyword_set(xtitle) eq 0 then xtitle=''
if keyword_set(ytitle) eq 0 then ytitle=''

if not keyword_set(xrange) then xrng=[0,nxm] $
                           else xrng=[min(xrange), max(xrange)]
if not keyword_set(yrange) then yrng=[0,nym] $
                           else yrng=[min(yrange), max(yrange)]

case 1 of 

                         title=title,/device, charsize=pcharsize, $
  keyword_set(noaxis): plot,[0,0],[0,0],/xstyle,/ystyle,position=pos,$
                         title=title,xtitle=xtitle,ytitle=ytitle,/device, $
                         xtickname=[" "," "],ytickname=[" "," "]

  else:                plot,[0,0],[0,0],/xstyle,/ystyle,title=title,/nodata,$

if keyword_set(position) then !p.multi=psave