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8.10 GR Object Identifier Conversion Functions
There are situations where it is necessary to convert, or map, one type of object identifier to another. One instance is when an image is to be attached to a vgroup, another is when an image's index must be obtained so that it can be passed to the
GRselect
routine to access the image, but all that is available is the image's reference number. The former instance requires a means of mapping a raster image identifier to a reference number, which in turn will be stored in a vgroup object. The latter instance requires a means of mapping an image's reference number to an index. The
GRidtoref
and
GRreftoindex
functions provide this functionality.
8.10.1 Mapping an Image Identifier to a Reference Number: GRidtoref
The
GRidtoref
routine takes one argument, an image identifier, and maps it to a valid reference number.
8.10.2 Mapping a Reference Number to an Index: GRreftoindex
The
GRreftoindex
routine takes two arguments, a file identifier and the reference number of an image, and maps them to an image index.
TABLE 8N GRidtoref and GRreftoindex Parameter List
Routine Name
(Fortran-77)
Parameter
Data Type
Description
C
Fortran-77
GRidtoref
(mgid2rf)
ri_id
int32
integer
Image identifier.
GRreftoindex
(mgr2idx)
gr_id
int32
integer
General raster data set identifier.
ref
uint16
integer
Reference number to be mapped.
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HDF User's Guide - 06/04/97, NCSA HDF Development Group.