coyote: CGIMAGEINFO

Description
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 `
 as an alternative to cgImageInfo.
Categories
Graphics
Params
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.
Examples
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
Author
FANNING SOFTWARE CONSULTING::
    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
History
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
Copyright (c) 2008-2011, Fanning Software Consulting, Inc.