To subscribe/unsubscribe to the hdfnews mailing list, please send your
request to ncsalist@ncsa.uiuc.edu with the appropriate command (e.g.
subscribe hdfnews, unsubscribe hdfnews, help) in the *body* of the message.

HDF Newsletter 42

May 26, 1999

CONTENTS

  • Release of Java Products v2.3
  • GR interface supports JPEG compression

  • Release of Java Products v2.3

    A new release of the HDF Java Products is now available from:
        http://hdf.ncsa.uiuc.edu/java-hdf-html/download.html
    
    This release includes many fixes and performance enhancements to the Java HDF Viewer and Java HDF Interface. This release also includes a complete implementation of the Java HDF Server, which supports transparent access to remote HDF files. The release includes pre-built binaries (including the HDF library) for several popular platforms, and full source code.

    For complete information, see:

       http://hdf.ncsa.uiuc.edu/java-hdf-html/
    
    Below is a list of new features in release 2.3 of the JHV. For a complete list of features, see the JHV User's Guide. (http://hdf.ncsa.uiuc.edu/java-hdf-html/jhv/index.html)
    1. Distributed with the newest released HDF library, HDF41r3.
    2. Significant performance improvement to handle larger datasets.
    3. Zoom in and out to navigate large images.
    4. All new and improved "spreadsheet" package.
    5. Transparent access to remote files with RMI server, servlet, or standalone server.
    6. Ability to modify and save spreadsheet data.
    7. A User Preferences Menu.
    8. Both 'bounding-box' and entry form selection of a subset of an SDS array or raster image.
    9. Field and record selections in the Vdata spreadsheet.
    10. Revised and updated Online User's Guide.
    The Java HDF products provide Java classes for reading and creating HDF files. These classes are designed to operate as a "data server" for HDF, accepting requests (Java objects describing what to read) and returning data and metadata from an HDF file (as Java objects). The Java HDF Viewer uses these classes to access HDF files on local disk.

    Starting with Release 2.3, the Java HDF Products also include classes to transparently access HDF files across a network. The HDF Java Products can be run as a server on any system that wishes to share the contents of HDF files with JHV clients across a network. The Java HDF Server contains exactly the same code as used in the Java HDF Viewer client, with additional code to send the request to a remote system and return the results as serialized Java objects via a network. Release 2.3 of the JHV contains the complete code for both the client and server.

    To access data on a remote system, the JHS must be installed and started. The Java HDF server can be configured in three different ways:

    1. A standalone server
      The server runs as a standalone program which listens on a socket.
    2. A Servlet
      The server runs as a Servlet, plugged in to a Java Web server.
    3. An RMI Remote Object
      The server is accessed as a Java object using the Java Remote Invocation Method (RMI).
    A JHV client can use none, any, or all of these methods to access HDF files on remote systems, depending on how the remote system's Java HDF Server is configured. In each case, the server functions identically, and the results returned are the same from each, and for files on local disk. The features and display are identical no matter where the HDF file is located.

    For more complete information about the Java HDF Server, see:

       http://hdf.ncsa.uiuc.edu/java-hdf-html/jhs/index.html
    
    

    GR interface supports JPEG compression

    Newsletter 41, announcing the release of HDF 4.1r3, failed to mention that the GR interface now supports JPEG compression. Using C, you can now use GRsetcompress to compress a GR image with JPEG compression. However, the Fortran counterpart to this function (mgscompress) does not support JPEG compression. We will be providing a new GR Fortran function that supports JPEG compression in the near future.