Top Document: JPEG image compression FAQ, part 1/2 Previous Document: [1] What is JPEG? Next Document: [3] When should I use JPEG, and when should I stick with GIF? See reader questions & answers on this topic! - Help others by sharing your knowledge There are two good reasons: to make your image files smaller, and to store 24-bit-per-pixel color data instead of 8-bit-per-pixel data. Making image files smaller is a win for transmitting files across networks and for archiving libraries of images. Being able to compress a 2 Mbyte full-color file down to, say, 100 Kbytes makes a big difference in disk space and transmission time! And JPEG can easily provide 20:1 compression of full-color data. If you are comparing GIF and JPEG, the size ratio is usually more like 4:1 (see "[4] How well does JPEG compress images?"). Now, it takes longer to decode and view a JPEG image than to view an image of a simpler format such as GIF. Thus using JPEG is essentially a time/space tradeoff: you give up some time in order to store or transmit an image more cheaply. But it's worth noting that when network transmission is involved, the time savings from transferring a shorter file can be greater than the time needed to decompress the file. The second fundamental advantage of JPEG is that it stores full color information: 24 bits/pixel (16 million colors). GIF, the other image format widely used on the net, can only store 8 bits/pixel (256 or fewer colors). GIF is reasonably well matched to inexpensive computer displays --- most run-of-the-mill PCs can't display more than 256 distinct colors at once. But full-color hardware is getting cheaper all the time, and JPEG photos look *much* better than GIFs on such hardware. Within a couple of years, GIF will probably seem as obsolete as black-and-white MacPaint format does today. Furthermore, JPEG is far more useful than GIF for exchanging images among people with widely varying display hardware, because it avoids prejudging how many colors to use (see "[8] What is color quantization?"). Hence JPEG is considerably more appropriate than GIF for use as a Usenet and World Wide Web standard photo format. A lot of people are scared off by the term "lossy compression". But when it comes to representing real-world scenes, *no* digital image format can retain all the information that impinges on your eyeball. By comparison with the real-world scene, JPEG loses far less information than GIF. The real disadvantage of lossy compression is that if you repeatedly compress and decompress an image, you lose a little more quality each time (see "[10] Does loss accumulate with repeated compression/decompression?"). This is a serious objection for some applications but matters not at all for many others. User Contributions: 1 chloroquineorigin ⚠ aralen for sale https://chloroquineorigin.com/ - aralen where to buy malarone buy chloroquine uk https://chloroquineorigin.com/ 2 eyytfb ⚠ May 6, 2022 @ 9:21 pm hydroxychloroquine classification https://keys-chloroquinehydro.com/ Comment about this article, ask questions, or add new information about this topic:Top Document: JPEG image compression FAQ, part 1/2 Previous Document: [1] What is JPEG? Next Document: [3] When should I use JPEG, and when should I stick with GIF? Part1 - Part2 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jpeg-info@uunet.uu.net
Last Update March 27 2014 @ 02:11 PM
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