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teem Riot-nrrd hackers unite
- Introduction
- General NRRD format description
- NRRD format definition
- Example NRRD files
- Compatible file formats
- Library description
- Kernels in Nrrd
- Demo of nrrd/unu uses
- Advocacy

Nearly Raw Raster Data

Nrrd is a library and file format designed to support scientific visualization and image processing involving N-dimensional raster data. Nrrd stands for "nearly raw raster data". Besides dimensional generality, nrrd is flexible with respect to type (8 integral types, 2 floating point types), encoding of written files (raw, ascii, hex, or gzip or bzip2 compression), and endianness (the byte order of data is explicitly recorded when the type or encoding expose it). Besides the NRRD format, the library can read and write PNG, PPM, and PGM images, as well as some VTK "STRUCTURED_POINTS" datasets. About two dozen operations on raster data are implemented, including simple things like quantizing, slicing, and cropping, as well as fancier things like projection, histogram equalization, and filtered resampling (up and down) with arbitrary seperable kernels.

This document aims to describe the NRRD file format and the nrrd library, which can read and write NRRD files. Various examples illustrate the variety of possible nrrd operations available in the nrrd library, which are also accessible from the command-line "unu" program. Impatient readers should look at "Example NRRD files", "Demonstrations using nrrd", and "Advocacy".

In these pages, "NRRD" refers to the file format, "Nrrd" refers to the C struct defined in nrrd.h, "Nrrd" refers to the library containing all the nrrd functions, and "nrrd" is a general term for all of these.