1.1 Overview
The Java™ HDF Viewer (JHV) is a Java-based visualization tool for
browsing NCSA Hierarchical Data Format (HDF) files.
JHV allows users to browse through any HDF file;
starting with a view of all top-level objects in an HDF file's hierarchy,
JHV allows a user to descend through the hierarchy and navigate among the
file's data objects.
The content of a data object is loaded only when the object is selected,
providing interactive and efficient access to HDF files.
The JHV user interface is designed to be easy to use and intuitive.
JHV was implemented by using Java that is designed to be machine-independent.
The interface and features are the same for all platforms.
The structure of the HDF file is displayed in a tree with data groups and
data objects represented as conventional folders and icons.
You can easily expand or collapse folders to navigate the
hierarchical structure of an HDF file.
1.2 JHV Features
JHV version 2.2 has the following features. Limitations on these features are listed in the next section.
- Loads HDF and ASCII files.
- Converts an ASCII file into an HDF file.
- Saves a data object into an HDF file or an ASCII file.
- Supports viewing scientific data sets (multidimensional arrays),
Vdata tables (record or tabular data tables), raster images,
palettes, attributes (text or numeric descriptions of a dataset
or macros), Vgroups (hierarchical grouping of data objects in
the file) and file annotations (text descriptions of a file).
- Lets users descend levels of each kind of HDF object and displays
information about objects, such as the dimensions of an SDS,
the names and values of its attributes, etc.
- Allows mouse-drag to select and display a subset of an SDS array
or raster image.
- Magnifies the display of a selected rectangular sub-region of an
image by a zoom factor.
- Displays the image pixel coordinates, dimensional scales, and
data/pixel values continuously as the mouse moves.
- Generates spreadsheet data from images or creates an image from
spreadsheet data.
- Does animations for 3D SDS or multiple 8-bit raster images.
- Makes transparent images and overlays 8-bit raster images.
- Changes an image palette and performs image manipulation such as
RGB color balance, contrast, smooth, image contour, etc.
- Creates XY-plots and histograms from images.
- Plots data columns from a Vdata table with different view options
and display styles.
- Shows data statistics and converts data with the general power
function, f(x) = Constant + Slope * x^Power.
- Shows data attributes in (name, value) table format.
- Opens the Online User's Guide.
1.3 Limitations
The current implementation of JHV has the following limitations.
Many of these limitations are scheduled for resolution in the
next JHV release, currently targeted for October 1998.
- Remote file access is not supported.
- JHV only loads/saves ASCII files which follow the
HDF ASCII Interchange Format.
- Loading a large ASCII file is very slow.
- Only one object (or subset) may be savesd to a file, i.e., saving multiple objects
is not supported.
- Updating or appending to an existing file is not supported.
- Saving an ASCII file does not save a color table for a raster image,
or dimension scales for an SDS.
- JHV only supports 2- or 3-dimensional SDSs. 1D SDSs cannot be
viewed.
- Opening a large image or data object may not work due to the
limitations of the Java virtual machine.
- Vdata fields with order 3 or above may be cut off in display.
- Copying and pasting image or spreadsheet data are not supported.
- Image overlay of planes of a 3D SDS is not supported.
1.4 System Requirements
To run JHV, a Java 1.1.x Virtual Machine, such as JDK-1.1.6, is required
and 24MB RAM is recommended. JHV version 2.2 has been built and is
available on the following platforms:
- Solaris
- Solaris-x86
- SGI IRIX 5.3
- SGI IRIX 6.2
- Linux
- Windows 95/NT
1.5 Installing and Running JHV
JHV is distributed from the
NCSA Java-based Products
page at http://hdf.ncsa.uiuc.edu/java-hdf-html/.
The JHV distribution is available in two forms:
-
A self-contained package, complete with the Java Runtime Environment (JRE).
This package can be installed and run with no other software. (About 18 MB)
-
A ready-to-run Java application, which can run on any system which
has Java installed. (About 3 MB)
- For UNIX systems, download and execute the self-installation shell program.
- For Windows 95/NT systems, download and execute the self-extracting archive.
In both cases, this step will install a JHV directory structure on your system.
The README file in the top level of that structure contains the following
instrctions for running JHV.
For the self-contained package, this is all than is needed.
For the ready-to-run package, the Java environment needs to be set up:
- UNIX environment
-
To run JHV on a UNIX system, first set the following environment variables:
CLASSPATH -- add the path to the NCSA JHI/JHV classes,
e.g. setenv CLASSPATH /usr/local/jhv/lib/classes.zip:$CLASSPATH
LD_LIBRARY_PATH -- add the path to the NCSA JHI/JHV libraries,
e.g. setenv LD_LIBRARY_PATH /usr/local/jhv/lib:$LD_LIBRARY_PATH
PATH -- add the path to the NCSA JHI/JHV binaries,
e.g. setenv PATH /usr/local/jhv/bin:$PATH
-
Then start JHV by typing
jhv at a command line prompt.
- Windows 95/NT environment
-
The following steps are required to run JHV on a Windows 95/NT system:
- Set the variable JHVHOME in the JHV batch file
jhv.bat
(in your_jhv_home\bin).
- If needed, set the variable JAVAHOME.
- Create a shortcut to the JHV executable, if desired.
- Start JHV by double-clicking on the executable icon or on the shortcut,
or by typing
jhv at the DOS command prompt.
- If you get the error message "Out of environment space" when running
jhv.bat under Windows 95, you need to set the
Initial Environment memory allocated to the command line to 4096 bytes
as follows:
- Open the Windows Explorer.
- Open the JHV home directory.
- Open the
bin directory.
- Right click on the
jhv.bat icon.
- Select Properties from the menu.
- Click the Memory tab.
- Find Initial Environment.
- Click the arrow next to the field.
- Scroll to and select 4096.
- Click OK .
For more information, see the instructions at the
