Routines (alphabetical) > Routines: H > HDF Routines > HDF_GR_IDTOREF

# HDF_GR_IDTOREF

This function returns the HDF reference number of the raster image identified by the parameter ri_id. This routine is commonly used for the purpose of annotating the raster image or including the raster image within an HDF Vgroup. The tag number for a GR is 306.

## Syntax

Result = HDF_GR_IDTOREF(ri_id)

## Return Value

Returns the HDF reference number of the raster image if successful or not found (0) otherwise.

## Arguments

### ri_id

Raster image identifier returned by HDF_GR_SELECT or HDF_GR_CREATE.

## Keywords

None

## Version History

5.2 | Introduced