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Chapter 1: Introduction

- 1.1 Overview
- 1.2 About This Release
- 1.3 Current Features

- 1.3.1 Browsing Features
- 1.3.2 Editing Features

- 1.4 Limitations/Known Problems
- 1.5 Further Information

## 1.1 Overview

The HDFView is a Java-based tool for browsing and editing HDF4 and HDF5 files. HDFView allows users to browse through any HDF4 and HDF5 file, starting with a tree view of all top-level objects in an HDF file's hierarchy. HDFView 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 HDF4 and HDF5 files. HDFView editing features allow a user to create, delete, and modify the value of HDF objects and attributes.

The HDFView graphical user interface (GUI) is simple and easy-to-use. First, HDFView was implemented by using the JavaTM 2 Platform, which is machine-independent. The GUI components have the same look-and-feel for all machines. Second, HDFView uses conventional folders and icons to display groups and datasets in a tree structure. Users can easily expand or collapse folders to navigate the hierarchical structure of an HDF file. Third, HDFView shows data content as text (table or plain text) or as image.

## 1.2 About This Release

This release includes bug fixes, new features,a test suite, and improved documentation.

To obtain the current version of HDFView, visit download and install HDFView

#### HDF libraries

This release was built and tested with HDF 4.2.5 and HDF5-1.8.4 Patch 1 with HDF5 1.6 compatibility flag. For information on new features in HDF5 Release 1.8.0 and format compatibility considerations, please visit http://www.hdfgroup.org/HDF5/doc/ADGuide/CompatFormat180.html.

#### Platforms

This release was built and tested for the following platforms:

##### 32-bit distribution -- runs on 32-bit systems or 64-bit systems with 32-bit JRE

- Linux
- Mac Intel
- Solaris
- Windows

##### 64-bit distribution -- runs on 64-bit systems with 64-bit JRE

- Linux x86_64
- Linux ia64
- Mac Intel
- Solaris 64-bit

#### Major Improvements

- Built on HDF5 1.8.4 Patch 1 library and HDF 4.2.5 library.
- Fix memory leak in the HDF-Java native.
- Add H5.getOpenIDCount() and H5. getOpenID() to track any open IDs.
These functions can be very useful for checking memory leak for applications.
- Add features to show data pointed to by object references or region references.
- Find/search dataset from HDFView.
- Add user option to open a file directly with read-only mode.
- Show unsigned 64-bit integer.
- Support netcdf3 files for the NETCDF module (ncsa.hdf.object.nc2.NC2File).

#### Major Bug Fixes

- HDFView: Incorrectly displays data-type: character array
- HDFView: if change palette then flip image, original colorscale is used
- Local version of HDFView doc has broken links etc.
- HDView: indices changed between 2.3 and 2.4. Why?
- HDFView does not show preceding spaces for attribute values that begin with spaces
- HDFView uses incorrect image values
- HDFView: "Show Value" is always 0 if show image for 32-bit unsigned array
- HDF4 object package failed on reading data
- Incorrect Size of variable length dataset
- Problem on import/export strings in compound datasets in HDFView
- HDFView doc does not mention can save to PNG, GIF, BMP
- HDFView: rainbow palette selection is different depending on where it is selected
- Remove HDFCDataTypes from web page
- HDFView: can't view contents of group if has same name as file
- HDFView - Get error if open a compound dataset with string and reference
- H5Sselect_hyperslab parameter order in header comment is wrong
- High dim label is wrong
- 16-bit and 32-bit images do not scale properly if set range
- Use better memory allocation in HDF4 JNI to avoid crash on OutOfMemory error on large dataset.
- Show some HDF-EOS attributes stored in HDF4 vdata.
- Fix a problem of displaying information for HDF4 vdata without name.
- Add HDF-Java logging levels to HDF5 JNI and set default level to "SEVERE".

## 1.3 Features

This version fixed bugs from previous versions and added a few new and enhanced features. It is a continuous work from the previous versions of HDFView. Some of the major features from previous versions include replaceable I/O and GUI modules, memory leak fixes, enhanced documentation, and test suite.

This version is user-configurable to support HDF4 or HDF5 or both. Users can choose HDFView features to support HDF4 or HDF5 or both when installing HDFView or compiling from the source code.

The following is a list of the browsing and editing features of HDFView. Details of the features are discussed in their related chapters.

### 1.3.1 Browsing Features

- Plugable GUI modules
  - Tree Viewer
  - Table Viewer
  - Image Viewer
  - Text Viewer
  - Metadata Viewer
  - Palette Viewer
- Supported file formats
  - HDF4
  - HDF5
  - netCDF (read only)
  - FITS (read only)
- Tree view of file structure
  - Supports drag-and-drop files to HDFView
  - Displays file hierarchy in a tree and allows users to navigate among the file's data objects
  - Adds options to show dataset as an image, a table or text
  - Allows users to select a subset of dataset to display
  - Shows attributes and other general information of data objects
  - Supports large fonts in GUI components
  - Adds -geometry switch to set the window size and location
- Table view of file content
  - Be able to show large dataset (e.g. 1,000,000 x 100); very fast in table viewer
  - Displays simple compound dataset (simple or nested) in table
  - Allows users to select fields/members of VData/compound dataset to display
  - Shows multi-dimension compound dataset
  - Displays line plot for selected table data
  - Views variable-length datasets
  - Views ENUM dataset
- Image view of file content
  - Filters out fill value from images
  - Imports and applies palette from an external file
  - Supports simple image manipulation: zooming image in/out, flipping image horizontally or vertically
  - Changes image brightness
  - Displays animation of 3-D images
  - Displays histogram for selected image area
  - Modifies palette for index RGB images
  - Supports multiple color tables for HDF5 images
  - Provides slider bar for modifying image threshold range
  - Filters "fill value" in Image Viewer
  - Shows actual palette that results from palette manipulation
  - Supports large number of 8kx8k 3-D images by reuse the memory data buffer
  - Incorporates Mouse Grab/Move to browse an image
- Text view of file content
  - Displays HDF5 user block in text, octal, hex, etc.
  - Provides option to show char dataset as text
  - Shows text attributes and text dataset in selected fonts (type and size)
  - Shows file information, such as file size and total number of datasets

### 1.3.2 Editing Features

- Convert JPEG, GIF, PNG, and BMP images to HDF5 or HDF4
- Save HDF4 or HDF5 images to JPEG, GIF, PNG, and BMP images
- Writes variable length string data
- Adds/deletes/renames datasets and groups
- Edits content of datasets
- Copies/pastes object in the same file or dross files of the same file format
- Exports dataset values to an ASCII text file
- Saves an HDF4/HDF5 image to a JPEG file
- Adds/deletes/modifies attributes
- Converts a JPEG image file into an HDF4/HDF5 file
- Imports data values from a text file
- Adds and modifies user blocks

## 1.4 Limitations / Known Problems

The current implementation of HDFView has the following limitations:

- HDFView does not support undo operations; all changes will go to the physical file, and the editing results cannot be recovered.
- Deleting object/attribute in HDF4 is not supported.
- HDFView does not support conversion between HDF4 and HDF5.
- HDFView supports only indexed image with RGB color model or 24-bit true color image. It does not support other color models such as CMYK and HSV.
- HDFView cannot modify compressed HDF4 SDS if rank is greater than 2 because the existing compression algorithms supported by HDF do not allow partial modification to a compressed datastream.
- HDFView cannot modify HDF4 vdata. HDF4 only writes vdata by records while hdf-java reads data by vdata fields since hdf-java does not support data structure of vdata record.
- Writing nested compound data of HDF5 is limited to some simple cases. HDFView does not write complex compound data.

## 1.5 Further Information

General information about HDF (HDF4 and HDF5) is available at http://www.hdfgroup.org/.

Information about the HDFView tool and related products is available at http://www.hdfgroup.org/hdf-java-html/

Questions and feedback may be sent to the HDF Helpdesk.

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##### Last Modified: December 16, 2008