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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.
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.
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.