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Vector graphics resources
XML and vector graphics
XML.com's articles lay it all out for you, including a feature-to-feature comparison of PGML and VML.
Web graphics activity
The W3C site that keeps you up-to-date on its vector graphics work.
XML and vector graphics formats
An excellent six-part series from XML.com that investigates the merits of each vector proposal before the W3C.
Flash Q&A
Macromedia answers your questions about the now-open Flash format.
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What it is
Most images on the Web today, including GIFs and JPEGs, are raster images (or bitmaps) that record the color of each pixel individually. Since they're locked into a static resolution, raster graphics resize and print poorly, but they are well-suited for photographs, where each pixel needs to be defined.
Vector graphics, on the other hand, record images as mathematical descriptions of lines, Bezier curves, and other geometric shapes. This object-oriented approach means they're not locked into an exact pixel count, and graphic artists can access each object independently.
Web builders can currently create vector graphics with common illustration programs, such as Adobe Illustrator, but those graphics must be converted to raster format for native support in Web browsers. Vector formats are supported on the Web via plug-ins such as Flash, but no official, vendor-neutral standard exists.
Why it's important
Currently, designers have to convert vector images to larger, raster formats for the Web, or they must make users download a plug-in to view the images online. An official vector graphics standard would give a big boost to vector graphics on the Web, eliminating the need for proprietary plug-ins and fixing the problems of existing raster formats, such as the lack of scalability.
Vector graphics are scalable because each image is recorded as a small instruction set and rendered on the user's computer. This means vector graphics can resize with browser windows, and they print better than static images do. This device-independence makes them well-suited for use on noncomputer browsers such as TV sets and personal digital assistants (PDAs).
Vector file sizes are also significantly smaller than traditional bitmap graphics, resulting in faster-loading pages. They're easily editable since you can access each object within the image individually, and they lend themselves to simple animation.
Where it's at (as of 11/3/98)
The W3C has spelled out the requirements for a future vector graphics standard, and it recently formed a working group to assess the viability of such a standard. The group has received several submissions that could accelerate this process, including PGML, VML, and WebCGM. (More on these below.)
| Vector graphics timeline |
| 5/96: |
W3C produces the requirements for a scalable graphics standard |
| 4/98: |
Macromedia opens Flash file format; Adobe and others propose PGML |
| 5/98: |
Microsoft and others propose VML |
| 8/98: |
Inso and others propose WebCGM |
And Macromedia plans to submit its Flash file format (SWF) to an undisclosed standards body, presumably the W3C, for consideration. With more than 40 million downloads in the past year, Flash is considered the de facto vector graphics standard on the Web. In an attempt to make it an official industry-wide standard, Macromedia opened its source code in April 1998, making it freely available to content and tools developers. Also a VML supporter, Macromedia believes an ASCII-based format and the binary-based Flash address different purposes and can coexist.
In the meantime, the W3C has published these vector graphics submissions for discussion (although they don't necessarily support each of them):
Precision Graphics Markup Language (PGML)
Submitted in April 1998 by Adobe and others, PGML defines a text-based markup language for vector graphics, based on Adobe's PostScript language and Portable Document Format (PDF). The proposed language also includes additional functionality for the Web, such as transparency, antialiasing, and support for simple animation. An application of XML, PGML defines a set of simple graphics objects--such as rectangles, circles, ovals, and pie wedges--and lets Web builders hand-code their graphics, although it will more likely be used to export graphics from within products such as Adobe Illustrator. PGML defines and manages its own coordinate system, and its strength lies in its expressive power. It also supports simple animation.
Vector Markup Language (VML)
VML was ubmitted in May 1998 by Microsoft and others. Like PGML, VML is an application of XML that describes a method for marking up vector graphics for the Web. Using text-based tags to define paths using connected lines and curves, VML uses a coordinate system based on the Cascading Style Sheet Level 2 (CSS2) model. VML is derived from the graphic model found in Microsoft Office's drawing tools, and it's likely to be deployed in Internet Explorer 5.0.
WebCGM
Submitted in August 1998 by the CCLRC and others, WebCGM proposes a simpler form of the Computer Graphics Metafile (CGM) standard especially for the Web. CGM, which has been a standard for complex schematics since 1987, is a binary format widely used for large-scale CAD drawings. This proposal would let the aerospace, automotive, and defense industries that currently use CGM to more effectively exploit the Web. WebCGM is a joint effort of the W3C and the CGM Open Consortium.
The Scalable Vector Group plans to draft its own XML-based vector format by mid-1999. Since the PGML and VML proposals compete with each other and overlap in some parts, the W3C plans to create a format that capitalizes on the strengths of both. Agreeing upon and implementing that could take a year or more.
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