JPEG

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JPEG

Computing a standard file format for compressing pictures by disposing of redundant pixels
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

JPEG

[′jā‚peg]
(graphic arts)
Graphics file format for compressed still images, particularly photographic images found on the World Wide Web; developed by the Joint Photographic Experts Group.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

JPEG

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

JPEG

(Joint Photographic Experts Group) An ISO/ITU standard for compressing still images. Pronounced "jay-peg," the JPEG format is very popular due to its variable compression range. JPEGs are saved on a sliding resolution scale based on the quality desired. For example, an image can be saved in high quality for photo printing, in medium quality for the Web and in low quality for attaching to emails, the latter providing the smallest file size for fastest transmission over slow connections.

Not Great for Text
JPEGs are not suitable for graphs, charts and explanatory illustrations because the text appears fuzzy, especially at low resolutions. Compressing images in the GIF format is much better for such material (see GIF).

JPEGs Are Lossy
Using discrete cosine transform, JPEG is a lossy compression method, wherein some data from the original image is lost. It depends on the image, but ratios of 10:1 to 20:1 may provide little noticeable loss. The more the loss can be tolerated, the more the image can be compressed.

Compression is achieved by dividing the picture into tiny pixel blocks, which are halved over and over until the desired amount of compression is achieved. JPEGs can be created in software or hardware, the latter providing sufficient speed for real-time, on-the-fly compression. C-Cube Microsystems introduced the first JPEG chip. See JPEG2000, JPE file and GIF.

File Extensions
JPEGs use the JPEG File Interchange Format (JFIF), and file extensions are .JPG or .JFF. M-JPEG and MPEG are variations of JPEG used for full-motion digital video (see MPEG). See graphics formats.


Saving JPEGs
At first glance, these two dialogs seem contradictory because the larger number means high quality in one and low quality in the other. Photoshop (top) uses a 1-to-12 scale for quality, while Epson (bottom) uses a percentage for the amount of compression. The more compression, the more loss in the result. Standard is the original JPEG format, while Optimized compresses more effectively. Progressive causes the image to display incrementally from top to bottom. Web users with slow connections see the image form on screen right away rather than wait for the entire file to download first.


Saving JPEGs
At first glance, these two dialogs seem contradictory because the larger number means high quality in one and low quality in the other. Photoshop (top) uses a 1-to-12 scale for quality, while Epson (bottom) uses a percentage for the amount of compression. The more compression, the more loss in the result. Standard is the original JPEG format, while Optimized compresses more effectively. Progressive causes the image to display incrementally from top to bottom. Web users with slow connections see the image form on screen right away rather than wait for the entire file to download first.
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References in periodicals archive ?
It shoots without hassle, delivers impeccable JPEGs, and even offers great versatility and diversity for RAW shooters to play around with.
Google has announced a new open source algorithm that will encode high-quality JPEG with 35 percent smaller files, without the loss of quality.
Raw photos, with data taken straight from the camera's image sensor, offer more editing flexibility and image quality than traditional JPEG images.
If you go to Steve's Fundraising Fuji Fotos Facebook page and see an image you like, simply choose your picture, donate to his fundraising page at justgiving.com/Steve-Morris11 and he'll send you the Jpeg for your personal use.
Submit all collateral materials on CDs with jpegs of entries clearly labeled.
When they get that magic photo, they don't want to risk capturing it on JPEG and not having it be as qood as it could be," he says.
It features maps, satellite images and driving directions, and enables users to pan and zoom over 3D images of landscapes and cities, rotate and tilt images and save them as a jpeg.
Worldwide Computer Products News-6 October 2004-Aladdin says its eSafe is only gateway-based product to protect against JPEG threats(C)1995-2004 M2 COMMUNICATIONS LTD http://www.m2.com
'But individuals are very unlikely to be directly affected, except by an increase in cost of products using jpegs.'
In a move more farcical than BT claiming to own hyperlinks (and, by the way, that judgment is expected any day now), Forgent Networks reckons it holds the patent for Jpegs. This would mean Forgent is owed 16 years of licencing fees.
JPEGs, on the other hand, have 10 ranges of compression available to the user.
A corresponding drawback, though, is that raw files take about 3 times the storage space as JPEGs -- typically about 15MB instead of 5MB in my tests with FV-5.