Plugging in to Visual Data

Abstract

Scientific data can be stored in several ways. A popular format used by NASA and other scientific groups worldwide is the Hierarchical Data Format (HDF). HDF provides a flexible file environment to store data in many ways, including database and image formats. HDF also supports superimposition of data onto maps or images, a popular method used by Earth scientists and others to display geographic and related information. Several software products enable opening and viewing of HDF-formatted files, but until recently users have been unable to access and manipulate HDF data with common software applications. The recent availability of a mountain of NASA's Landsat 7 data in HDF format ([edcwww.cr.usgs.gov/][1]) has made this shortcoming apparent. Fortunately, Fortner Software, developers of Noesys, has released a tool for importing HDF data into Adobe Photoshop ( ). The HDF Import Plug-in consists of two files that users install easily by dragging them into the import/export folder within the Adobe Photoshop plug-ins folder. Upon starting Photoshop, HDF files can be brought into Photoshop easily by selecting HDF Import from the import submenu of the file menu. Visual HDF data formats (called data objects) supported by the plug-in include 8- or 24-bit raster images, two-dimensional (2D) datasets, and 2D projections (called slices) of data from a multidimensional dataset. Up to seven dimensions of data can be “sliced” by the HDF Plug-in and shown as a 2D image. Figure 1 illustrates how Photoshop can be employed to display three-dimensional HDF data using the red, green, and blue (RGB) color channels. The gray-scale images in the figure represent intensities of light seen by a satellite sensor as it viewed Earth through three different ranges of wavelengths. The top left image depicts data taken at a wavelength at the blue end of the visual spectrum. The top right image is the same view in the middle of the visual spectrum (green). The bottom left image is at the red end of the spectrum. By assigning each of these views to a red, green, or blue channel in Photoshop, the three-colored image (lower right) can be easily created. Because the user controls which data are displayed in which channel, specific features can be colored as desired. For example, the water in the image could be shown as shades of red instead of blue. It is a distinct advantage to be able to open HDF images in Photoshop. Dozens of Photoshop options for manipulating and enhancing visual features give users the ability to present data in almost any way they choose. The HDF Import Plug-in only works to visualize data; Photoshop contains no tools for analyzing data. Still, the HDF Import Plug-in will be welcomed by anyone trying to optimize presentation of visual data using Adobe Photoshop. The plug-in works well, installs easily, and showed no bugs in this testing with Photoshop 5.0 on a Macintosh. [1]: http://edcwww.cr.usgs.gov/