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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.