HDF is a multi-object file format that facilitates the transfer of various types of scientific data
between machines and operating systems. See http://www.hdfgroup.org/release4/platforms.html for a list
of platforms currently supported.
HDF allows self-definitions of data content and easy extensibility for future enhancements or
compatibility with other standard formats. HDF includes Fortran and C calling interfaces, and utilities
for manipulating, viewing, and analyzing data in HDF files. The HDF library contains interfaces for
storing and retrieving compressed or uncompressed 8-bit and 24-bit raster images with palettes, n-
Dimensional scientific datasets and binary tables. An interface is also included that allows arbitrary
grouping of other HDF objects.
HDFRasterImages
HDF supports the storing of both 8-bit and 24-bit raster images. Beside storing information about the
dimensions and palette of a raster image, HDF supports raster image compression. In previous versions of
HDF (DF interfaces,) Run-length encoding and Imcomp compression were both supported. The currently
supported compression methods include simple RLE, N-bit, Skipping huffman, Gzip, Szip, and JPEG.
Although no longer support Imcomp compression, the library can read images with Imcomp compression.
HDFScientificDataSets
Scientific Data Sets (SDSs) are useful for storing n-Dimensional gridded data. The actual data in the
dataset can be of any of the "standard" number types: 8, 16 and 32bit signed and unsigned integers and 32
and 64bit floating point values. In addition, a certain amount of meta-data can be stored with an SDS
including:
o The coordinate system to use when interpreting or displaying the data.
o Scales to be used for each dimension.
o Labels for each dimension and the dataset as a whole.
o Units for each dimension and the data.
o The valid max and min values for the data.
o Calibration information for the data.
o Fill or missing value information.
o Ability of having more than one file open at a time.
o A more general framework for meta-data within the SDS data-model
(allowing 'name = value' style meta-data.)
o Support for an "unlimited dimension" in the SDS data-model, making
it possible to append planes to an array along one dimension.
HDFAnnotations
Any object in an HDF file can have annotations associated with it. There are a number of types of
annotations:
o Labels are assumed to be short strings giving the "name" of a
data object.
o Descriptions are longer text segments that are useful for giving
more indepth information about a data object
o File annotations are assumed to apply to all of the objects in a
single file.
HDFVsetInterfaces
The Vset module provides interfaces to two basic HDF building blocks. Vgroups are generic grouping
elements allowing a user to associate related objects within an HDF file. As Vgroups can contain other
Vgroups, it is possible to build a hierarchical file. Vdatas are data structures made up of fields and
records. Data is organized into "fields" within each Vdata. Each field is identified by a unique
"fieldname". The type of each field may be any of the basic number types that HDF supports. Fields of
different types may exist within the same Vdata.
By combining Vdatas in Vgroups it is possible to represent higher level data constructs: mesh data,
multi-variate datasets, sparse matrices, finite-element data, spreadsheets, splines, non-Cartesian
coordinate data, etc.
HDFandnetCDF
Starting with HDF version 3.3, netCDF v.2.3.2 of Unidata is supported with the SD multifile interface. SD
and netCDF interfaces can read both netCDF files and multi-dimensional arrays (SDS) stored in the HDF4
files transparently. For more information, see Chapter 3, "Scientific Data Sets", of the HDF User's
Guide.
To disable netCDF interfaces in the HDF library, configure the library using --disable-netcdf flag and
rebuild it.
EXAMPLES
All HDF routines require the header "hdf.h" to be included in the C source file, unless if the SD
routines are used, then the header "mfhdf.h" should be included instead.
Fortran programs should use "dffunc.inc" for all interfaces, "mffunc.inc" for the SD interfaces, and
"hdf.inc" for non-SD interfaces.
To compile a program that makes HDF calls on most Unix platforms.
(FORTRAN):
{HDFLIBDIR}/bin/h4fc myprog.f
(C):
{HDFLIBDIR}/bin/h4cc myprog.c
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