QuickStudy: Anti-aliasing
Computerworld - Anti-aliasing smooths the raw and haggard edges on digital type and images on computer and handheld displays, wireless phones, printers, even digital cameras.
Aliasing - jagged or stair-stepped edges - appears when there are too few pixels in an image or on a display to represent it realistically.
Spectral aliasing - moire or herringbone patterns where none should be - appears as a result of interference between digital signals, such as color and brightness.
How It Works
In graphics or type, anti-aliasing algorithms sample, or examine and evaluate, the colors and shades of pixels adjoining curved or diagonal lines. They also shade some pixels to create a softer line. The eye no longer clearly sees the stair-stepped edge and, paradoxically, it reads the softer line as clearer.
Some anti-aliasing algorithms create a similar effect by jittering. Instead of changing a pixel's color or tone, the filter slightly offsets, or jitters, the pixel by a random amount from its normal placement. This creates a more gradual transition between an object and its background.
Dithering, or creating a similar shaded effect using patterns of dots of colors, can create an anti-aliasing effect for photographs and shaded drawings.
Increasing the resolution and thus reducing the pixel size can create an effect similar to that of anti-aliasing, but this may not always be feasible.
Fractal compression lets you store thousands of large image files on a single CD.
Fractal compression works by reducing each shape or pattern to an equation. When the fractal image is reconstructed, there's often more information than the display can show, and artifacts - bits of white debris - are created. Anti-aliasing eliminates these artifacts and creates smoother edges.
High-end graphics hardware maker Silicon Graphics Inc. in Mountain View, Calif., developed an anti-aliasing method that uses special accumulation buffers that temporarily store rendered frames. When several frames have accumulated, the graphics chip blends them together.
To counter aliasing, some devices, such as Intel Corp.'s Pentium III chip and many printers and digital cameras, incorporate anti-aliasing filters. High-end graphics cards may contain more sophisticated anti-aliasing filters.
Most anti-aliasing filters sample adjoining pixels between two and 16 times at different locations, then combine and average the different readings to get the most realistic color. More samples result in subtler gradations between image edges and along curved or diagonal lines and type. But a higher sample rate takes more time and memory.
Some cards use supersampling, which renders the image at a resolution higher than the display can support and then scales down and filters the image - in effect, adding new pixels, before sending it to the display. But such brute-force techniques take a toll on performance.



- Excel 2010 Cheat Sheet
- Register for this Computerworld Insider Cheat Sheet and gain access to hundreds of premium content articles, guides, product reviews and more.
- Forrester Total Economic Impact (TEI) Case Study - Oracle
- In this paper, Forrester Consulting examines the total economic impact and potential return on investment (ROI) realized by three Enterprise organizations as they...
- The Hidden Truth About Virtualizing Business-Critical Applications
- This IDG whitepaper highlights key findings based on the Quickpoll Survey conducted with more than 300 Enterprise and Commercial IT decision makers worldwide...
- Top 10 Myths About Virtualizing Business-Critical Applications
- Even though virtualization has brought positive change to enterprise IT over the last decade, some skepticism remains about how valuable virtualization can be...
- Enterprise Java Applications on VMware: Unix to Linux Migration Guide
- This guide focuses on key considerations for IT Architects who are in the process of migrating Java applications from UNIX to Linux as...
- Virtualizing Tier 1 Applications: A Critical Step on the Journey Toward the Private Cloud
- This IDC white paper explains how much of the Enterprise IT community is at a crossroads in extending their journey to the private... All Applications White Papers
- Live Webcast
Banish Poor Application Performance: Eliminate Business Disruptions, Increase End User Productivity - End User Experience, 30-Min Webinar
Wed. Feb. 22nd ~ 11 AM ET
Are you ready to gain the proactive ability to rapidly respond... - Apps QuickStart Series Part 2: Designing and Deploying SQL Server on VMware vSphere
- Download this webcast to learn about the design considerations for virtualizing SQL workloads, performance and scalability information and high-availability options, as well as...
- Apps QuickStart Series Part 1: Designing and Deploying Exchange 2010 on VMware vSphere
- Download this webcast to learn the virtual hardware design considerations for Exchange 2010, deployment using the building block approach, options for high-availability and...
- Virtualize Business-Critical Applications with Confidence
- Virtualizing business-critical applications has become a key focus for organizations as they move along their virtualization journey. With the launch of VMware vSphere®...
- Discover the Benefits of Virtualization for Federal Applications
- Want to say goodbye to missed SLAs? VMware can help you virtualize mission-critical applications such as Oracle, MS Exchange and SharePoint to achieve...
- Reduce Application Lifecycle Management Costs with VMware ThinApp
- Traditional desktop application deployment and management is a time-consuming and costly endeavor for IT. From development to deployment, including help desk support, the... All Applications Webcasts