Data and Image Compression

Compression is a way of encoding digital data so it takes up less storage space and requires less network bandwidth to be transmitted. There are two basic types of compression: lossy methods, in which some data is lost when the files are decompressed, and lossless methods, in which no data is lost when the files are restored to their original format.

By Lee Copeland

August 21, 2000 12:00 PM ET

Computerworld - As long as bandwidth is expensive and people are impatient, data compression is here to stay. Simply put, compression methods crunch data - text, graphics, audio or video - into a computer-decipherable shorthand that's 10% to 99% of its original size. The data takes up less storage space and requires less bandwidth to be transmitted over the Internet. In addition, many methods can squeeze multiple files into a single file called an archive.

There are two basic methods for compressing data: lossy and lossless. Lossless techniques compress data without destroying or losing anything during the process. When the original document is decompressed, it's bit-for-bit identical to the original. Lossy techniques let the file be compressed even smaller, but some data is lost forever.

			Compression Standards Joint Photographic Experts Group (JPEG): A still-image, lossy compression method that uses discrete cosine transform equations to compress images at a ratio of up to 20-to-1, without noticeable loss. Lempel-Ziv-Welch: This algorithm, used in many compression formats, including graphics interchange format and Tag Image File Format, takes each input sequence of bits of a given length and creates an entry in a lookup table, along with a shorter code. Lookup entries are part of the compressed file, enabling the decoding program to rebuild the table. Moving Pictures Experts Group (MPEG): A lossy compression method for video. MPEG-1 is used for CD-ROMs and video CDs. MPEG-2 compresses video for regular and high-definition television. MPEG Audio Layer 3 (MP3): An audio compression technology that's part of MPEG-1 that uses perceptual audio coding to compress CD-quality audio by a factor of 12. Fractal: A lossy compression method for color images that's well suited for natural objects, with compression ratios up to 100-to-1. PKZip: A popular lossless compression shareware program from PKWare Inc. The program uses an algorithm and a data library to encode or archive multiple date files. PKUnzip decompresses the files to their original states. Wavelet: This form of lossy compression uses a mathematical function that can compress images to a greater extent than other methods - sometimes to only one-fourth the size of a similar image compressed with JPEG. Windows Media Technology: This Microsoft Corp. product delivers better sound quality than MP3 for same-size files, as well as near-DVD-quality video. - Lee Copeland and Russell Kay

"Lossy compression makes a trade-off: You give up accuracy for higher compression," says Steve Hoffenberg, director of product management at Sound Vision Inc., a digital imaging firm in Framingham, Mass. "If you're compressing bank records, you want to be sure they're identical before and after. But with an image or audio or video files, it's generally not crucial to restore every bit of data."

Recommend Digg Twitter ShareThis

Email Print Send Feedback Reprints

Additional Resources

Xerox

Win a color printer!

By using solid ink technology only from Xerox, you could save up to 65% by printing color for the cost of black and white. Enter for a chance to WIN a PhaserTM 8860 network color printer!

Microsoft

Upgrade to Internet Explorer 8 today.

Save time and mitigate security risk. Deploy it now.

Sybase

NEXT-GENERATION MOBILITY PLATFORMS

In this white paper, IDC analyzes the role of next-generation mobile enterprise platforms as organizations seek a more strategic deployment of mobile solutions.

Learn the important issues you must consider before starting your next mobility initiative. Get your mobility white paper from IDC now, compliments of Sybase.

White Papers & Webcasts

iPhone for the Enterprise
One of the biggest concerns of using the iPhone for the enterprise is the security and manageability issues. Read this white paper to...

IDC Webcast: Linux Adoption in a Global Recession
Join Al Gillen from IDC and Michael Applebaum from Novell in this on-demand webcast to see how Linux has emerged as an even...

2009 Gartner Magic Quadrant Report
Truly understand your options for WAN Optimization Controllers...

Bringing Order and Security to your Mobile Workforce: Corporate Mobility Policy and Device Management
(Source: Nokia) In many businesses, mobile devices are managed the way that laptops were managed ten years ago - as a kind of...

Tech Horizons: ASG's metaCMDB, The Technology That Rocks
Improved business productivity often requires more efficient IT and more efficient IT cannot be achieved without a better understanding of the way business...

Strategic ECM Webinar
Learn what new strategic business benefits can be realized through ECM!...

The Vector Approach to Data Center Power Planning
This white paper describes an approach that considers the major milestones and thresholds in data center power requirements-and how planners should adjust their...

Managing And Protecting Your Ever Increasing Mobile Assets
Learn best practices for desktop and application virtualization, computer security, and computer life-cycle management....

Yankee Group Mobile WAN Optimization Report
Mobile work continues to evolve. Learn how to keep up with the demands of your organization's mobile workforce....

5 Architecture Issues that Impact BES performance
This Live webinar will identify critical log file errors, performance counters, and configurations to pay close attention to when optimizing BES server performance....

All White Papers | All Webcasts