Progressive Image Transmission:

Delivering large images over slow networks faster and better

9 seconds

11 seconds

14 seconds

20 seconds

45 seconds

2 min. 21 sec.

8 min. 44 sec.

14 min. 34 sec.

X-ray image of the Sun from the Yohkoh satellite, courtesy of J. Lemen.

The Progressive Image Transmission (PIT) system delivers large digital images over slow networks in a small fraction of the time usually needed. Viewers get a good view in as little as 1/100th of the expected download time, at which point they can interact with the server by outlining rectangular regions of interest, which will be delivered losslessly at a higher priority. The user controls the lossiness of the image, which is not chosen in advance by the server.

PIT supports 24-bit true-color images as well as 16-bit gray-scale data. The algorithms used are quantitatively well behaved; the pixel statistics are preserved even for the early versions of the image. This provides good visual fidelity for general users and good numerical fidelity for professional users.

System Requirements
Unix workstation running Linux. IRIX, Solaris, or Ultrix. Any Java 1.1 platform.
For a demonstration copy, contact Dr. Jeffrey W. Percival (,
Space Astronomy Laboratory
University of Wisconsin - Madison
1150 University Ave.
Madison, WI 53706