Features of the JHV


The JHV is an interactive tool to visualise and analyse an HDF file. The JHV allows users to browse through any HDF file, starting with a view of the file that shows all top-level objects in its hierarchy, then lets them descend through the hierarchy and navigate among its various data objects. The objects include: file annotations, raster images, scientific dataset, vdata and vgroups. Any single object can be examined in detail.

The features included in the current release (2.0) are:

  1. Description of an HDF File
  2. Hierarchy of an HDF File
  3. User interface
  4. Display of 2D image
  5. Animation of 3D array
  6. Manipulation of SDS
  7. Display of pixel coordinates and data values
  8. Spreadsheet based-browsing of data values
  9. Zooming, sub-setting
  10. Image contour
  11. Image processing
  12. Palette editor
  13. Table browsing and xy-plots

Description of an HDF File

JHV allows user to descend levels of each kind of HDF objects and displays the information about objects, such like the dimensions of an SDS and the names and values of its attributes, etc.

Hierarchy of an HDF File

The structure of the HDF file is displayed in a tree with each type of object represented as an icon. You can expand or collapse node to navigate the hierarchical structure of an HDF file.

User interface

The JHV user interface is designed to be easy to use and intuitive. The JHV was implemented by using Java that is designed to machine-independent, the interface and features are the same for all platforms.

Display of 2D image

For 2-D arrays (SDS or raster images) the JHV displays a sub-sampled image. The user may select to look at the image in its full resolution in a separate window. A rectangular region of the image may be selected for viewing or analysis.

Animation of 3D array

In order to examine the images in the third dimension of 3-dimentational data array, JHV provides a capability to display the image in sequence like a movie. An "animation" option to step through the first dimension of the array, with controls for animation speed, single stepping, and backward and forward animation.

Manipulation of scientific dataset(SDS)

When data from an SDS is displayed as an image, the range of data values to display can be limited. This is useful to retrieve the region of interest and tell user which data values are more sensitive for the image of data.

Display of pixel coordinates and data values

In the image window, the pixel coordinates and data values at the mouse cursor are be displayed continously.

Spreadsheet based-browsing

For a specified rectangular subregions of an image, the data values may be displayed in a "spreadsheet". The user can select cells of the "spreadsheet" and the corresponding box of the image is highlighted.

Zooming, sub-setting

The JHV can magnify the display of rectangular subregions by a zoom factor. For xy-plots this may let user preview the change of parts of the data range or the whole column within the meta-data.

Image contour

JHV allows user to draw the contour over the raster image by different levels.

Image processing

JHV provides a collection of image filters which can be applied to the image. The image filters are similar to those provided by the popular `xv' utility, which include: "negative", "emboss", etc.

Palette editor

The palette editor is used to create and manipulate new color palettes (color tables) to better visualise images and data. A palette may be created and edited by using drawing tools in three separate component panel which replaces red, green and blue.

The fiddle option performs a linear compression and expansion on the palette and this is useful to produce greater colour variation on the image of data in region of interest.

Table browsing and xy-plots

Tabular data in an HDF file can be viewed as spreadsheet. This may include Vdata and objects in Vgroup. The user just may select one or more columns by clicking on the column name from the spreadsheet. An XY plot may be generated for the selected columns The XY-plot changes as the user moves the scrollbar and zooms.


HDF Group
NCSA

hdf-java@ncsa.uiuc.edu