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  The purpose of this program is allow interactive inquiry of image
  position and values for images displayed with cgImage.
  After a call to cgImage, cgImageInfo can be called and the user
  can use the cursor to click in the image display window. If the user clicks
  inside the image, the image location and value will be printed out in the
  user's IDL console window. The cgImageInfo program blocks the IDL command
  line until the RIGHT mouse button is clicked in the image display window.
  This cgImageInfo program is designed to work for the last image displayed with cgImage
  on a Windows or X device. Precautions are taken to help you avoid shooting
  yourself in the foot, but I can't anticipate every action a user might take at the
  IDL command line. Pay particular attention to exiting the program with the RIGHT mouse
  button before you close or kill the current graphics window. Failure to do so will
  put you into a very strange and precarious state from which no rescue is possible.
  You might want to consider using the Catalyst Program `IMGWIN <http://www.idlcoyote.com/catalyst/imgwin.html>`
  as an alternative to cgImageInfo.




    image: in, required,
        A 2D or 3D image array. Values will be returned from this image.
        In versions of IDL < 8.0, it is possible to use a HASH object of
        keys/images where this program will describe the value for each of
        the images in the HASH object.
    position: in, optional, type=float
        A four-element floating array giving the position of the image in
        the display window. If not provided, the image position will be
        retrieved from the last image position used with cgImage.


    To display an image with axes and then inquire about it::
        filename = FILEPATH(SUBDIR=['examples','data'], 'worldelv.dat')
        image = BYTARR(360,360)
        OPENR, lun, filename, /GET_LUN
        READU, lun, image
        FREE_LUN, lun
        thisPosition = [0.1, 0.1, 0.9, 0.9]
        cgImage, image, /KEEP_ASPECT, POSITION=thisPosition, /AXES
        cgImageInfo, image


          David W. Fanning
          1645 Sheely Drive
          Fort Collins, CO 80526 USA
          Phone: 970-221-0438
          E-mail: david@idlcoyote.com
          Coyote's Guide to IDL Programming: http://www.idlcoyote.com


    Change History::
      Written by: David W Fanning, 16 March 2008.
      Added ability to specify position directly in call. 20 March 2008. DWF
      Changed cursor operation to conform with expected differences
        between Windows and UNIX. 20 March 2008, DWF.
      Slightly modified screen directions. 16 November 2010. DWF.
      Modified so that multiple images/grids can be described 18 May 2011. MHS


    Copyright (c) 2008-2011, Fanning Software Consulting, Inc.

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