JPEG (Joint Photographic Experts Group)
The Joint Photographic Experts Group (JPEG) format is widely used and the JPEG standard is the most important image data compression standard. JPEG is a bitmap format commonly used to display photographs and other continuous-tone images in web pages on the Internet. Unlike the GIF format, JPEG retains all the color information in an RGB image. JPEG also uses a compression scheme that effectively reduces file size by identifying and discarding extra data not essential to the display of the image. Opening a JPEG image automatically decompresses it.
Because it discards data, the JPEG compression scheme is referred to as lossy. This means that once an image has been compressed and then decompressed, it will not be identical to the original image. A higher level of compression results in lower image quality, while a lower level of compression results in better image quality. In most cases, compressing an image using the Maximum quality option produces a result that is indistinguishable from the original.
The JPEG compression level is adjustable. Higher settings produce a larger file size with higher image quality (and visa versa). Typically, we have found that compression ratios of 10:1 or 15:1 produces generally acceptable results for photographic type images. For example, a 640 x 480 x 24-bit image is almost 1MB; the same 15:1 compressed image is only 61K!!!!.
JPEG does not work well with solid colors, 16 color images, drawings, cartoons etc. Use GIF instead.
JPEG2000 - The JPEG compression standard used in digital cameras and software starting in 2002. It features higher compression but with less image quality loss.
Note: You can use .jpg or .jpe or .jpeg as the extension at the end of the filename. Windows will recognise it as JPEG.
Technical stuff
JFIF
This is the JPEG File Interchange Format.
Progressive JPEG
This is a JFIF format that is useful for transmitting images, because the first part of the file contains the full dimensions of the image. Therefore, in a paint-while-load routine, you can display the whole image, then progressively clarify it as the rest of the file loads.
JTIF
This is the JPEG Tagged Interchange Format.
