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8.3 The GR Interface

 The GR consists of routines for storing, retrieving, and manipulating the data in GR data sets.

8.3.1 GR Interface Routines

All C routine names in the GR interface have the prefix "GR" and the equivalent FORTRAN-77 routine names are prefaced by "mg". All GR routines are classifiable within one of the following categories:

The GR routines are listed in the following table and described further in subsequent sections of this chapter.

TABLE 8A - GR Library Routines

Purpose
Routine Name7
Description
C
FORTRAN-77
Access
 GRstart mgstart Initializes the GR interface (Section 8.5.1 on page 266)

GRcreate mgcreat Creates a new raster image (Section 8.5.1 on page 266)

GRselect mgselct Selects the raster image (Section 8.5.1 on page 266)

GRendaccess mgendac Terminates access to the raster image (Section 8.5.2 on page 266)

GRend mgend Terminates access to the GR interface (Section 8.5.2 on page 266)

Raster Image Manipulation
 GRgetattr mggnatt/ mggcatt Reads an attribute of a raster image or a file (Section 8.9.4 on page 278)

GRidtoref mgid2rf Maps a raster image identifier to a reference number (Section 8.8.3 on page 275)

GRnametoindex mgn2ndx Maps the name of a raster image name to an index (Section 8.8.3 on page 275)

GRreadimage mgrdimg/ mgrcimg Reads raster image data (Section 8.7.1 on page 272)

GRreftoindex mgr2idx Maps the reference number of a raster image to its index (Section 8.8.3 on page 275)

GRsetattr mgsnatt/ mgscatt Assigns an attribute to a raster image or a file (Section 8.9.2 on page 277)

GRwriteimage mgwrimg/mgwcimg Writes raster image data (Section 8.6.2 on page 269)

GRreqimageil mgrimil Sets the interlace mode of the image read for subsequent read operations (Section 8.7.2 on page 273)

LUT Manipulation
 GRgetlutid mggltid Gets a palette identifier given the palette's index (Section 8.10.1 on page 279)

GRluttoref mglt2rf Maps a palette identifier to a reference number (Section 8.10.2 on page 280)

GRreadlut mgrdlut/ mgrclut Reads palette data from a raster image (Section 8.10.6 on page 281)

GRwritelut mgwrlut/ mgwclut Writes palette data to a raster image (Section 8.10.4 on page 280)

GRreqlutil mgrltil Sets the interlace mode of the next palette for subsequent read operations (Section 8.7.2 on page 273)

Maintenance
 GRsetcompress mgscomp Specifies whether the raster image will be stored in a file as a compressed raster image (Section 8.6.2 on page 269)

GRsetexternalfile mgsxfil Specifies that the raster image will be written to an external file (Section 8.6.3.1 on page 270)

Inquiry
 GRattrinfo mgatinf Retrieves information about an attribute (Section 8.9.3 on page 277)

GRfindattr mgfndat Finds the index of a data object's attribute given an attribute name (Section 8.9.3 on page 277)

GRfileinfo mgfinfo Retrieves the number of raster images and the number of global attributes in the file (Section 8.8.1 on page 274)

GRgetiminfo mggiinf Retrieves general information about a raster image (Section 8.8.2 on page 274)

GRgetlutinfo mgglinf Retrieves information about a palette (Section 8.10.3 on page 280)

Chunking
 GRsetchunk mgschnk Creates chunked raster image (Section 8.11.1 on page 283)

GRgetchunkinfo mggichnk Retrieves information about a chunked raster image (Section 8.11.2 on page 284)

GRsetchunkcache mgscchnk Sets maximum number of chunks to be cached (Section 8.11.3 on page 285)


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HDF User's Guide - 07/21/98, NCSA HDF Development Group.