Demo Images

This page contains links to monochrome compressed images. Their sizes are not so large, so that you can download them in a reasonable time even with a 56K modem connection.

We have chosen not to show color images here. Why? Because some differences could be attributed to the color processing only, and not to the coding method.

Important warning:

If you are using a monitor that can display only 256 or even 65K colors, the images may not look right! You may see awful "banding" artifacts in the recovered images. This happens because some browsers will use much less than 256 gray levels (even though they could use more). This problem could be quite easily solved with mild dithering, or a program that displays more gray levels, and by no means represents a limitation of the compression method. So, we decided to keep the images assuming that they will be seen with the appropriate programs and monitor setup.

Comparison with JPEG

Here we present side-by-side some images compressed with JPEG (using xv) and with SPIHT to exactly the same file size. We won't tell which is which, and we ask you to pick your favorite and tell us. Please also inform if you are certain that vinyl LPs do sound better than CDs, and/or looked at the images with a CGA monitor.

Lena 512 x 512 @ 0.31 bpp: SPIHT PSNR = 35.12 dB, JPEG PSNR = 31.8 dB (quality factor 15%).

Subjective Evaluation

This is a serious subjective evaluation test for reconstructed images. Click below to see one image that was compressed with SPIHT, together with its original. You have 10 seconds to decide which one is the original. Be warned that all your reactions are being carefully monitored, and don't try to cheat zooming the image! And don't touch the monitor with your nose either!

Lena 512 x 512 @ 0.5 bpp: PSNR = 37.12 dB.
Lena 512 x 512 @ 1.0 bpp: PSNR = 40.41 dB.

Links to other pages.

SPIHT Home Page;
Properties of the Method
Licensing Information
Demo Programs
Technical Discussion
WWW Image Compression Resources
Guest Book

These pages are still under construction. Sorry for any inconvenience...