The WRITE_NRIF procedure writes an image and its color table vectors to an NCAR Raster Interchange Format (NRIF) rasterfile.
WRITE_NRIF only writes 8- or 24-bit deep rasterfiles of types “Indexed Color” (8-bit) and “Direct Color integrated” (24-bit). The color map is included only for 8-bit files.
See the document “NCAR Raster Interchange Format and TAGS Raster Reference Manual,” available from the Scientific Computing Division, National Center for Atmospheric Research, Boulder, CO, 80307-3000, for information on the structure of NRIF files.
This routine is written in the IDL language. Its source code can be found in the file write_nrif.pro in the lib subdirectory of the IDL distribution.
Syntax
WRITE_NRIF, File, Image [, R, G, B]
Arguments
File
A scalar string containing the full path name of the NRIF file to write.
Image
The byte array to be written to the NRIF file. If Image has the dimensions (n,m), an 8-bit NRIF file with color tables is created. If Image has the dimensions (3,n,m), a 24-bit NRIF file is created, where each byte triple represents the red, green, and blue intensities at (n,m) on a scale from 0 to 255. The NRIF image will be rendered from bottom to top, in accordance with IDL standards.
R, G, B
The Red, Green, and Blue color vectors to be used as a color table with 8-bit images. If color vectors are supplied, they are included in the output (8-bit images only). If R, G, B values are not provided, the last color table established using LOADCT is included. If no color table has been established, WRITE_NRIF calls LOADCT to load the grayscale entry (table 0).
Note: WRITE_NRIF does not recognize color vectors loaded directly using TVLCT, so if a custom color table is desired and it is not convenient to use XPALETTE, include the R, G, and B vectors that were used to create the color table.
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