NB: The use of PNG representation files is deprecated in favor of fits2fits large file support. See Dealing with Large Files for more information.

X-ray archives present special problems for displaying data. Instead of images pixels, X-ray data files consist of detected photons stored in FITS binary tables. These can be hundreds of megabytes in size, regardless of the image dimensions. Downloading (and then binning) these tables on the fly can be painfully slow.

To remedy this situation, JS9 supports a special PNG representation file, explicitly tied to the original FITS file. The idea is that you can create a representation image from the original FITS data and use that file for display in JS9, while still supporting server-side analysis using the original file.

Other benefits include:

• The compressed PNG representation file will be decompressed automatically by the browser's optimized PNG support code.
• The representation file takes less memory than a downloaded FITS image.
• PNG files can be generated statically or dynamically.
• PNG files can be tailored to the specific observation (compare the 3c58 files).

See The PNG Representation File for more information.

JS9 Demos:

• the basics
• setting the size of the JS9 display
• menubar styles
• web page control
• preloading images into JS9

• multiple instances of JS9
• control multiple displays with one menu
• creating a JS9 instance dynamically
• syncing images in multiple displays

• adding plugins to JS9
• the imexam plugin
• pan and zoom
• overlaying catalogs
• dynamic selection of displays

• image blending
• RGB composite images
• creating new colormaps

• remote data analysis
• running tasks when a region changes

• displaying different FITS datatypes
• support for large FITS files

• using the all-in-one files
• PNG representation files vs FITS files