MGHGRDENSITYIMAGE__DEFINE
Class Name
      MGHgrDensityImage
Purpose
  
   This class implements a density plot as an IDLgrImage.
Category
      Object graphics.
Superclasses
  
   This class inherits from IDLgrImage.
Properties
  
   The following properties are available, in addition to supported by IDLgrImage:
          BYTE_RANGE (Init,Get) 
      
       The range of byte values to which the data range is to be mapped.
          COLORSCALE (Init) 
      
       A reference to an object (like a color bar or another density
      
       plane) from which default colour mapping information
      
       (BYTE_RANGE, DATA_RANGE and PALETTE) can be retrieved.
          DATA_RANGE (Init,Get) 
      
       The range of data values to be mapped onto the indexed color
      
       range. Data values outside the range are mapped to the nearest
      
       end of the range. If not specified, DATA_RANGE is calculated
      
       from the range of data values the first time the data values
              are assigned. 
    
     DATA_VALUES (Init,*Get,Set) 
      
       A 2-D array of data (interpreted as floating point) to be displayed.
      
       The DATA_VALUES keyword is accepted by GetProperty if & only if the
              STORE_DATA property has been set.
          PALETTE (Init,Get,Set) 
      
       A reference to the palette defining the byte-colour mapping.
          STORE_DATA (Init,Get): 
      
       This property determines whether the data values are stored
      
       with the object. The default is 1 (values are stored); it
      
       can be overridden by setting STORE_DATA to 0 when the object
              is created. 
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    This software is provided subject to the following conditions:
    1.  NIWA makes no representations or warranties regarding the
    
     accuracy of the software, the use to which the software may
    
     be put or the results to be obtained from the use of the
    
     software.  Accordingly NIWA accepts no liability for any loss
    
     or damage (whether direct of indirect) incurred by any person
          through the use of or reliance on the software.
    2.  NIWA is to be acknowledged as the original author of the
    
     software where the software is used or presented in any form. 
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Modification History
  
   Mark Hadfield, 1998-08: 
          Written. 
  
   Mark Hadfield, 2000-12: 
          Complete overhaul.
      Mark Hadfield, 2004-05: 
    
     Revised code to use IDL 6.0 features. Removed call to MGH_GET_PROPERTY.