;       Version 1, Liyun Wang, NASA/GSFC, October 19, 1994
;          Incorporated into the CDS library
;       Version 2, Liyun Wang, NASA/GSFC, November 18, 1994
;          Added features of rotating a point or a region;
;          All conversions of coordinate systems are done via CNVT_COORD
;             routine, common block IMG_SCALE is removed;
;          Added the capability of fitting the limb and finding the center of
;             the solar disc
;       Version 2.1, Liyun Wang, NASA/GSFC, December 23, 1994
;          Made rasters plotted against the displayed image with
;             respect to the time when the image was shot.
;       Version 2.2, Liyun Wang, NASA/GSFC, December 27, 1994
;          Added feature of plotting grids parallels and meridians on
;             the solar disc
;       Version 3, Liyun Wang, NASA/GSFC, January 25, 1995
;          Generized the pointing widget base siutable for any SOHO instrument
;          Separated codes for pointing and limb-fitting from the main
;             program code.
;          Take out the CDS_RASTER keyword parameter, replaced it with a more
;             general keyword parameter POINT_STC.
;       Version 3.1, Liyun Wang, NASA/GSFC, February 28, 1995
;          Made it capable of reading FITS files that have binary tables
;          Pointing can be done in a zoomed-in window now
;          Added elliptical limb fitting option
;       Version 3.2, Liyun Wang, NASA/GSFC, March 15, 1995
;          Image displayed with axes around it if data coordinate system can
;             be established
;          Pointing criteria is imposed if the pointing area has to be off limb
;          User is warned if any of the pointing area is not pointed
;       Version 3.3, Liyun Wang, NASA/GSFC, April 27, 1995
;          Added GIF output option
;       Version 3.4, Liyun Wang, NASA/GSFC, May 9, 1995
;          Added feature of differentially rotating forward (backward)
;             points on the east (west) limb
;          Made start time and image obsvervation time editable
;          Added feature of box-shaped cursor
;          Made it capabile of reading in GIF images (useful when only
;             the GIF format of the latest solar images are available)
;          Started using the new version of XGET_SYNOPTIC (which has no
;             COMMON blocks in its main and event handler routines)
;          Allowed the user to select FITS files from his/her own
;             directory
;          Added option to set relative size of displayed image
;       Version 3.5, Liyun Wang, NASA/GSFC, May 15, 1995
;          Improved the on-line help system
;       Version 3.6, Liyun Wang, NASA/GSFC, May 31, 1995
;          Added feature of locking up image orientation so that
;             coordinates of the image follow any image manipulation
;             operation
;          Added feature of stacking images for easy retreiving
;          Made cursor be markable via the middle or right mouse button
;       Version 3.7, August 10, 1995, Liyun Wang, NASA/GSFC
;          Allowed the string of image source or image type to be shown
;       Version 3.8, August 16, 1995, Liyun Wang, NASA/GSFC
;          Made it possible to directly access the SOHO summary data
;          Can enter coordinates of a point and show it on the image
;          Added the capability of modifying FITS headers to include
;             the scaling and solar center info from the limbfitting result
;       Version 3.9, October 10, 1995, Liyun Wang, NASA/GSFC
;          Started using XPS_SETUP to handle making hard copies in PS format
;       Version 4.0, October 23, 1995, Liyun Wang, NASA/GSFC
;          Made images saved in the stack retrievable via image icons
;          Made the default starting directory for loading GIF files
;             or personal FITS files be current working directory
;          Removed the option to retain loaded images in a separate window
;          Added option for cursor tracking
;       Version 4.1, November 2, 1995, Liyun Wang, NASA/GSFC
;          Added interface for loading in personal image files
;          Added display for position angle of the cursor
;       Version 4.2, November 15, 1995, Liyun Wang, NASA/GSFC
;          Added image smooth and edge detect option
;          Made image profile to be shown in draw widget window
;       Version 4.3, November 27, 1995, Liyun Wang, NASA/GSFC
;          Added image-overlay feature
;       Version 4.4, December 28, 1995, Liyun Wang, NASA/GSFC
;          Added feature to allow pointing structure to be sent to and
;             received from planning tool
;       Version 4.5, February 26, 1996, Liyun Wang, NASA/GSFC
;          Private data path can be default to PRIVATE_DATA if this env
;             variable is defined
;          Fixed bug that IDL working dir may be changed when navigating
;             through "personal" data paths
;          Boxed cursor is now default to that reflecting the actual
;             pointing area defined in POINT_STC
;          Modified such that upon loading a new image, current zoommed-in
;             image is zoommed out implicitly
;       Version 4.6, March 5, 1996, Liyun Wang, NASA/GSFC
;          Changed button labels for image time and study time
;          Fixed a bug data type being unrecorded
;          Automatically scaling and loading correct color table of
;             the SOHO EIT images
;          Added SOHO EIT color tables in color table list
;          Added an image manipulating button for log scaling the image
;       Version 4.7, March 12, 1996, Liyun Wang, NASA/GSFC
;          Added a switch button to control point of view (Earth or SOHO)
;          Better identified image type and source
;          Point of view is set automatically when loading a new image
;       Version 4.8, March 13, 1996, Liyun Wang, NASA/GSFC
;          Added feature of better adjusting color table without
;             calling XLOADCT
;       Version 4.9, March 19, 1996, Liyun Wang, NASA/GSFC
;          Added an option of plotting a raster position over the
;             displayed image
;          Fixed a bug in reading a new column from a FITS file with
;             binary tables
;          Fixed a bug in changing directory path and filter for
;             selecting personal data
;       Version 4.10, March 27, 1996, Liyun Wang, NASA/GSFC
;          Added interface to SOHO private data directory
;          Made it more robust when loading a new file
;       Version 4.11, April 1, 1996, Liyun Wang, NASA/GSFC
;          Added the FOV keywords for plotting a fixed field of view
;          Added check against the attemp of trying to rotate a point
;             or region which is outside the solar disc
;          Added RADIUS tag in the CSI structure
;          Utilized a new widget program for adjusting arbitrary study
;             or imaging time
;          Added advanced/novice mode switching feature
;       Version 4.12, April 19, 1996, Liyun Wang, NASA/GSFC
;          Added widget window dump option for machines running UNIX
;          Fixed a few bugs in Pointing Tool
;          Applied EIT degridding algorithm
;       Version 4.13, May 29, 1996, Liyun Wang, NASA/GSFC
;          Fixed problem when run on a 24-bit color display
;       Version 4.14, July 15, 1996, Liyun Wang, NASA/GSFC
;          Auto log scaled images from Yohkoh SXT, MLSO, PDMO
;       Version 4.15, August 28, 1996, Liyun Wang, NASA/GSFC
;          Fixed a problem that CRPIX1 and CRPIX2 was treated as the
;             reference pixel based on (0,0), should be (1,1) all the
;             time as in the FITS specification
;          Zoomed-in image is displayed with a better scale
;       Version 4.16, December 4, 1996, Liyun Wang, NASA/GSFC
;          Removed restriction of switching images on stack while in
;             zoom-in mode
;          Added option button to over plot MDI high-res field of view
;          Added option to dump main image window in PS format
;       Version 4.17, December 6, 1996, Liyun Wang, NASA/GSFC
;          Added option to remove a selected image from image stack
;       Version 4.18, February 11, 1997, Liyun Wang, NASA/GSFC
;          Added option to spawn an image window and to quit with
;             image window retained
;          Added option to rotate points on central meridian
;       Version 4.19, February 20, 1997, Liyun Wang, NASA/GSFC
;          Added "Recover" button when called from the Planning Tool
;          Removed novice/advanced mode
;       Version 4.20, March 6, 1997, Liyun Wang, NASA/GSFC
;          Implemented differential rotation indicator for any constant
;             longitudinal points and points at the same Solar X value
;          Replaced the "Recover" button with "Refresh" when not
;             called from the Planning Tool (and "Refresh Display" is
;             removed from the "Misc" menu in this case)
;       Version 4.21, April 1, 1997, Liyun Wang, NASA/GSFC
;          Allowed OBS_TIME field to be editable
;          Fixed a bug occurred during plotting off_limb rasters
;       Version 4.22, June 3, 1997, Liyun Wang, NASA/GSFC
;          Modified such that pointing is updated if called again
;             with another pointing structure while IMAGE_TOOL is
;             still running
;          Improved cursor plotting scheme
;       Version 4.23, July 30, 1997, Liyun Wang, NASA/GSFC
;          Added AUTO_PLOT keyword to be used with POINT_STC input keyword
;       Version 5.0, September 8, 1997, Liyun Wang, NASA/GSFC
;          Major changes on interface as well as on functionality:
;          1) Put all available tools under one pull down menu "Tools"
;          2) Simplified the procedure to zoom in/out and to position
;             the FOV box in Poiting Tool (by getting rid of call to
;             BOX_CURSOR)
;          3) Made XGET_SYNOPTIC as a built-in tool
;          4) Added Overlayer Tool
;          5) Improved ploting on image icons as well as in zoom-in window
;          6) Added option to save current image in FITS format
;          7) Adopted cw_loadct for color table manipulating
;          8) Changed and enhanced CSI tag names to conform with the
;             FITS standards 
;          9) Allowed read GIF format and save it in FITS format
;         10) Greatly improved functionality of differential rotation
;         11) Made full-disk differential rotation available
;         12) Added contour plot option under Image Manipulation
;         13) Avoided rebuilding pull-down button when switch back to
;             image originated from a FITS file with binary table
;         14) Special treatment to overcome an IDL 5.0 bug that causes
;             the whole widget window growing whenever a new image is loaded
;	Version 5.1, October 13, 1998, William Thompson, NASA/GSFC
;	   Limit the special treatment for the window growing problem mentioned
;	   above to IDL 5.0, and treat IDL 5.1 and above as before.
;	Version 6, 14-July-2003, William Thompson, GSFC
;	   Use environment variable SOHO_ORIENT for MDI field-of-view.