JPEG description

JPEG at a Glance

Stands for
Joint Photographic Experts Group
File extension
.jpg, .jpeg, .jpe, .jif, .jfif, .jfi
Inventors
Eric Hamilton, Joint Photographic Experts Group, Tom Lane,
Independent JPEG Group
Created
1990 (JPEG), 1991 (JFIF)
Standards
ISO/IEC 10918
Colors & bit depth
maximum 16,777,215 colors
8 bit grayscale, 24 bit true color , 12 bit
Transparency
None
Optional Goodies
Progressive rendering
Chroma subsampling
Detail smoothening
Color profiles (ICC) support
Metadata support (ICC, EXIF, IPTC)
Compression
Lossy – JPEG compression (lossy discrete cosine transform
followed by Huffman coding).
How it works
JPEG compression is designed to reduce things that don’t make a
noticeable difference in the picture. It’s based on studies of
human perception, and it throws away data you won’t notice.
Links

In computing, JPEG (pronounced JAY-peg; IPA: /ˈdʒeɪpɛɡ/) is a commonly used method of compression for photographic images. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10 to 1 compression with little perceivable loss in image quality.

JPEG is the most common image format used by digital cameras and other photographic image capture devices, and is the most common format for storing and transmitting photographic images on the World Wide Web.

JPEG is good for

Photographs

In fact, this is the intended usage for JPEG images. Most digital cameras save by default in this format.  When you’ve got an image that looks mostly like a photograph, JPEG will nearly always do the best job for you. Note that JPEG compression is lossy, and this is not the best way to keep the maximum quality of photos. Furthermore, the quality degrades at each re-compression, so watch out for multiple editing of JPEGs.

Images with many colors (more than 256 colors)

It is worth trying also PNG for these images, either paletized using quantization or true color.

JPEG Is Bad For

Text or black/white scans

Images with sharp edges

Drawings, cartoons, images with few colors

Advanced graphics programs will let you turn off chroma sub-sampling, and while you’ll pay a price in image size, these kind of images may look better with no/less chroma sub-sampling.

Images with transparency

JPEG does not support transparency. In these cases GIF or PNG are the alternatives.

Posted in Optimization Tips
2 comments on “JPEG description
  1. Very good application in relation to that even I have tried. And above all fast. Riot Since I spend all my photos anymore.

  2. daunjava says:

    Thanks for the tools my friend, I’ve been use that in some case. Your tools is very intuitive, gave all the changes in realtime with size output, i love that.

    Regards,
    Kharis

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