Progressive Transmission of Digital Images

Dr. Jeffrey W. Percival, Senior Scientist, Space Astronomy Laboratory

Dr. Richard L. White, Associate Astronomer, Space Telescope Science Institute.

Example of Progressive Image Transmission using our techniques.

This page shows the dramatic improvement in network speed using our technique of Progressive Image Transmission. We chose an astronomical image of stars and galaxies, which has 800 rows and 800 columns. This is large compared to images currently being sent over the Web.

The picture on the left shows the fraction of an image received after 60 seconds using a 2400 baud modem and the traditional sequential method of transmission. Only a tiny sliver of the image has been received, at the bottom. The picture on the right is the same image, also after 60 seconds using a 2400 baud modem, but this time using our method of Progressive Image Transmission.

Our technique uses a mathematical algorithm known as a wavelet transform to rearrange the image data in such a way that the important information can be extracted and sent first, followed by the vastly larger amount of irrelevant data. The image improves as time passes, ultimately resulting in an exact transfer of the original image.

In our method the user can stop the process when the image is good enough, which for large images can occur in only a tenth or a hundredth of the normal transmission time. This technique can speed up Web browsing, and allow much larger images to be sent over conventional phone lines than is practical now.

For more information, visit our web site.