NAME

       PDL::IO - An overview of the modules in the PDL::IO namespace.

SYNOPSIS

        # At your system shell, type:
        perldoc PDL::IO

DESCRIPTION

       PDL contains many modules for displaying, loading, and saving data.

       •   Perlish or Text-Based

           A few IO modules provide Perl-inspired capabilities.  These are PDL::IO::Dumper and
           PDL::IO::Storable.  PDL::IO::Misc provides simpler routines for dealing with delimited files, though
           its capabilities are limited to tabular or at most 3-d data sets.

       •   Raw Format

           PDL has two modules that store their data in a raw binary format; they are PDL::IO::FastRaw and
           PDL::IO::FlexRaw.  They are fast but the files they produce will not be readable across different
           architectures.  These two modules are so similar that they could probably be combined.

       •   Data Browsing

           At the moment, only PDL::IO::Browser provides data browsing functionality.

       •   Image Handling

           PDL has a handful of modules that will load images into piddles for you.  They include
           PDL::IO::Dicom, PDL::IO::FITS, PDL::IO::GD, PDL::IO::Pic, and PDL::IO::Pnm.  However, PDL::IO::FITS
           should also be considered something of a general data format.

       •   Disk Caching

           Both PDL::IO::FastRaw and PDL::IO::FlexRaw provide for direct piddle-to-disk mapping, but they use
           PDL's underlying mmap functionality to do it, and that doesn't work for Windows.  However, users of
           all operating systems can still use PDL::DiskCache, which can use any desired IO read/write
           functionality (though you may have to write a small wrapper function).

       •   General Data Storage Formats

           PDL has a number of modules that interface general data storage libraries.  They include PDL::IO::HDF
           and PDL::IO::NDF (the latter is now a separate CPAN module).  There is a PDL::IO::IDL, though at the
           moment it is not distributed with PDL.  PDL::IO::FITS is something of a general data format, since
           piddle data can be stored to a FITS file without loss.  PDL::IO::FlexRaw and PDL::IO::FastRaw read
           and write data identical C's low-level "write" function and PDL::IO::FlexRaw can work with FORTRAN 77
           UNFORMATTED files.  FlexRaw and Storable provide general data storage capabilities.  Finally, PDL can
           read Grib (weather-data) files using the CPAN module PDL::IO::Grib.

       •   Making Movies

           You can make an MPEG animation using PDL::IO::Pic's wmpeg function.

       Here's a brief summary of all of the modules, in alphabetical order.

   PDL::DiskCache
       The DiskCache module allows you to tie a Perl array to a collection of files on your disk, which will be
       loaded into and out of memory as piddles.  Although the module defaults to working with FITS files, it
       allows you to specify your own reading and writing functions.  This allows you to vastly streamline your
       code by hiding the unnecessary details of loading and saving files.

       If you find yourself writing scripts to procss many data files, especially if that data processing is not
       necessarily in sequential order, you should consider using PDL::DiskCache.  To read more, check the
       PDL::DiskCache documentation.

   PDL::IO::Browser
       The Browser module provides a text-based data browser for 2D data sets.

       It uses the CURSES library to do the scrolling, so if your operating system does not have the cureses
       library, you won't be able to install this on your machine.  (Note that the package containing the header
       files for the CURSES library may be called "libcurses" or possibly "libncurses".)

       PDL::IO::Browser is not installed by default because it gives trouble on Mac OS X, and not enough is
       known to fix the problem.  If you want to enable it, edit the perldl configuration file and rebuild PDL.
       To learn more about editing the configuration file, see the INSTALLATION section in the FAQ.  (Also, if
       you are familiar with CURSES on Mac, your help would be much appreciated!)

       To see if the module is installed on your machine (and to get more information about PDL::IO::Browser),
       follow this link or type at the system prompt:

        perldoc PDL::IO::Browser

       If you want to get more information about PDL::IO::Browser and it's not installed on your system, I'm
       afraid you'll have to pick out the pod from the source file, which can be found online at
       <http://pdl.git.sourceforge.net/git/gitweb.cgi?p=pdl/pdl;a=blob_plain;f=IO/Browser/browser.pd;hb=HEAD>.

   PDL::IO::Dicom
       DICOM is an image format, and this module allows you to read image files with the DICOM file format.  To
       read more, check the PDL::IO::Dicom documentation.

   PDL::IO::Dumper
       Provides functionality similar to Data::Dumper for piddles.  Data::Dumper stringifies a data structure,
       creating a string that can be "eval"ed to reproduce the original data structure.  It's also usually
       suitable for printing, to visualize the structure.

       To read more, check the PDL::IO::Dumper documentation.  See also PDL::IO::Storable for a more
       comprehensive structured data solution.

   PDL::IO::FastRaw
       Very simple module for quickly writing, reading, and memory-mapping piddles to/from disk.  It is fast to
       learn and fast to use, though you may be frustrated by its lack of options.  To quote from the original
       POD:

       "The binary files are in general NOT interchangeable between different architectures since the binary
       file is simply dumped from the memory region of the piddle.  This is what makes the approach efficient."

       This creates two files for every piddle saved - one that stores the raw data and another that stores the
       header file, which indicates the dimensions of the data stored in the raw file.  Even if you save 1000
       different piddles with the exact same dimensions, you will still need to write out a header file for each
       one.  You cannot store multiple piddles in one file.

       Note that at the time of writing, memory-mapping is not possible on Windows.

       For more details, see PDL::IO::FastRaw.  For a more flexible raw IO module, see PDL::IO::FlexRaw.

   PDL::IO::FITS
       Allows basic reading and writing of FITS files.  You can read more about FITS formatted files at
       <http://fits.gsfc.nasa.gov/fits_intro.html> and <http://en.wikipedia.org/wiki/FITS>.  It is an image
       format commonly used in Astronomy.

       This module may or may not be installed on your machine.  To get more information, check online at
       <http://pdl.sourceforge.net/PDLdocs/IO/FITS.html>.  To see if the module is installed on your machine,
       follow this link or type at the system prompt:

        perldoc PDL::IO::FITS

   PDL::IO::FlexRaw
       Somewhat smarter module (compared to FastRaw) for reading, writing, and memory mapping piddles to disk.
       In addition to everything that FastRaw can do, FlexRaw can also store multiple piddles in a single file,
       take user-specified headers (so you can use one header file for multiple files that have identical
       structure), and read compressed data.  However, FlexRaw cannot memory-map compressed data, and just as
       with FastRaw, the format will not work across multiple architectures.

       FlexRaw and FastRaw produce identical raw files and have essentially identical performance.  Use
       whichever module seems to be more comfortable.  I would generally recommend using FlexRaw over FastRaw,
       but the differences are minor for most uses.

       Note that at the time of writing, memory-mapping is not possible on Windows.

       For more details on FlexRaw, see PDL::IO::FlexRaw.

   PDL::IO::GD
       GD is a library for reading, creating, and writing bitmapped images, written in C.  You can read more
       about the C-library here: <http://www.libgd.org/>.

       In addition to reading and writing .png and .jpeg files, GD allows you to modify the bitmap by drawing
       rectangles, adding text, and probably much more.  The documentation can be found here.  As such, it
       should probably be not only considered an IO module, but a Graphics module as well.

       This module provides PDL bindings for the GD library, which ought not be confused with the Perl bindings.
       The perl bindings were developed independently and can be found at GD, if you have Perl's GD bindings
       installed.

   PDL::IO::Grib
       A CPAN module last updated in 2000 that allows you to read Grib files.  GRIB is a data format commonly
       used in meteorology.  In the off-chance that you have it installed, you should read PDL::IO::Grib's
       documenation.

   PDL::IO::HDF, PDL::IO::HDF5
       Provides an interface to HDF4 and HDF5 file formats, which are kinda like cross-platform binary XML
       files.  HDF stands for Heierarchicl Data Format.  HDF was originally developed at the NCSA.  To read more
       about HDF, see <http://www.hdfgroup.org/>.  Note that HDF5 is not presently distributed with PDL, and
       neither HDF4 nor HDF5 will be installed unless you have the associated C libraries that these modules
       interface.  Also note that the HDF5 library on CPAN is rather old and somebody from HDF contacted the
       mailing list in the Fall of 2009 to develop new and better HDF5 bindings for Perl.

       You should look into the PDL::IO::HDF \fIs0(4) documentation or PDL::IO::HDF5 documentation, depending
       upon which module you have installed.

   PDL::IO::IDL
       Once upon a time, PDL had a module for reading IDL data files.  Unfortunately, it cannot be distributed
       because the original author, Craig DeForest, signed the IDL license agreement and was unable to negotiate
       the administrative hurdles to get it published.  However, it can be found in Sourceforge's CVS attic, and
       any PDL user who has not signed IDL's license agreement can fix it up and resubmit it.

   PDL::IO::Misc
       Provides mostly text-based IO routines.  Data input and output is restricted mostly to tabular (i.e. two-
       dimensional) data sets, though limited support is provided for 3d data sets.

       Alternative text-based modules support higher dimensions, such as PDL::IO::Dumper and PDL::IO::Storable.
       Check the PDL::IO::Misc documentation for more details.

   PDL::IO::NDF
       Starlink developed a file format for N-Dimensional data Files, which it cleverly dubbed NDF.  If you work
       with these files, you're in luck!  Check the PDL::IO::NDF documentation for more details.

   PDL::IO::Pic
       Provides reading/writing of images to/from piddles, as well as creating MPEG animations!  The module uses
       the netpbm library, so you will need that on your machine in order for this to work.  To read more, see
       the PDL::IO::Pic documentation.  Also look into the next module, as well as PDL::IO::GD.

   PDL::IO::Pnm
       Provides methods for reading and writing pnm files (of which pbm is but one).  Check the PDL::IO::Pnm
       documentation for more details.  Also check out the previous module and PDL::IO::GD.

   PDL::IO::Storable
       Implements the relevant methods to be able to store and retrieve piddles via Storable.  True, you can use
       many methods to save a single piddle.  In contrast, this module is particularly useful if you need to
       save a complex Perl structure that contain piddles, such as an array of hashes, each of which contains
       piddles.

       Check the PDL::IO::Storable documentation for more details.  See also PDL::IO::Dumper for an alternative
       stringifier.

COPYRIGHT

       Copyright 2010 David Mertens (dcmertens.perl@gmail.com). You can distribute and/or modify this document
       under the same terms as the current Perl license.

       See: http://dev.perl.org/licenses/