Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!gistdev!flint From: flint@gistdev.gist.com (Flint Pellett) Newsgroups: comp.graphics Subject: Re: JPEG compression: "press release" Message-ID: <1058@gistdev.gist.com> Date: 21 Jan 91 19:07:01 GMT References: <1984@umriscc.isc.umr.edu> <11623@pt.cs.cmu.edu> <2908@sixhub.UUCP> Organization: Global Information Systems Technology Inc., Savoy, IL Lines: 44 davidsen@sixhub.UUCP (Wm E. Davidsen Jr) writes: >| 6. Why should the net convert to JPEG? >| >| Principally, to reduce bandwidth and storage requirements for posted >| images. JPEG images can be at least a factor of 4 smaller than GIF images >| with hardly any visible change in image quality; factors of 7 to 10 are >| achievable with not a lot of quality loss (the resulting images are still >| much better than many that I've seen posted). > Unfortunately I don't believe that this will redsuce net bandwidth as >much as you would believe. My feeling is that as long as there is any >visible loss of resolution people will see something interesting in >JPEG and then a posting in GIF format will appear. I also doubt very seriously if this effort is going to result in any reduction in net bandwidth. (But I DO hope you go ahead with the work: the other reasons are more than enough to justify it!) I tend to believe this is likely due to several temptations: 1. The temptation to post both a GIF and a JPEG version. 2. The temptation to post the same JPEG image 2 or 3 times, at 2 or 3 different quality levels. 3. The temptation for someone, after seeing an initial posting of an image at a low quality level, to create and post the same image at a higher quality level that is more satisfactory in their view. 4. The temptation to post more images, since each one is now smaller. (If you've got 100 images from the Hubble, for example, you might post the 10 best GIF images of 150K each. With JPEG, you will be tempted to post the best 40 JPEG images of 40K each. I won't argue which way is better, I only point out that the bandwidth used may turn out to be the same.) 5. The temptation to not be willing to accept ANY loss in quality. For some images (such as things like Hubble images, perhaps), any further loss in the quality of the image (that could be avoided) is unacceptable. -- Flint Pellett, Global Information Systems Technology, Inc. 1800 Woodfield Drive, Savoy, IL 61874 (217) 352-1165 uunet!gistdev!flint or flint@gistdev.gist.com