One of the advantages of SVG over some other graphics capability is the fact that SVG is vector-based. A vector graphic means that images are created via *recorded mathematical primitives (circle, line, square, etc.) rather than based on fixed pixels. Because SVG is a vector graphic, the same image can be sized very small or very large and remain crisp and bright regardless of the size. Typically the image has a smaller file size, too.
This doesn't seem like a big deal if the image is placed in a weblog post, and statically sized. My own use of SVG at this site is statically sized and I could just as easily use JPEGs or PNGs, other than the fact that I recreate the images based on the header graphic. However, over at the main Burningbird site, I'm experimenting around with using SVG as a resizable background element, and it's this use that truly demonstrates why SVG can be such an advantage over bitmap images.
Consider computer monitors and the problems we've always had about differing monitor sizes. Either our content seems to extend beyond the edges of the browser, generating a horizontal scroll bar. Or it's a skinny little bar in the midst of a vast expanse of blank space. Even if we use a background image and repeat it, we still end up with a mind numbing expanse of *nothing*.
As an alternative to the static, repeating background image, I used an SVG image I found at the Open Clip Art site, sized dynamically in the background, and statically in both the header and footer. For the background image, attributes on the SVG element provide further instructions in how the image is resized, and whether to maintain perspective or to have the image fill the given space. Right now, I have turned off the perspective, and the result is interesting when viewed in different sized windows.
Providing a dynamically sized background image is a fairly new use for SVG, so it's not without challenges. Opera on the Mac has problems with the resizing, as well as the gradients used in the image; Safari has problems with the gradient, though Webkit works nicely. However, I originally tried this approach using an external SVG file, incorporated into the page using the object element, but WebKit had problems with the object element. At this time, Firefox 3b3 is the only browser that manages both the gradient and the sizing, in addition to SVG inline or linked externally. I expect, though, that all three–Safari, Opera, and Firefox–will do well with using SVG for a background image in their next released versions.
As for IE, the entire site shows up primarily in black and white. The site is so plain, in fact, that I have a link labeled, "Why is this page so plain", to a page explaining my use of SVG that only shows up when the site is accessed by IE. As I'll be incorporating SVG into all of my sites, I'll be continuing my "B&W" support for IE to all the sites, rather than restrict access with the XHTML MIME type, as I originally did with this site.
Apple announced that it will be supporting SVG in the version 2.0 of the iPhone SDK because, according to a story on the topic, SVG is a resolution-independent image format that is highly compressible. The three variations of the same image at Burningbird demonstrate the resolution independence, with the image looking good in the site footer, the larger header image, and the potentially very large background.
Once I've debugged why the image isn't loading using the object element in Safari/Webkit, I could use one external gzipped SVG file, and eliminate most of the size constraints. The only restriction with using an external SVG file is that using the object element for the background can cause some odd behavior with IE. In addition, from a drawing performance perspective, I also found the inline SVG to be the best of the two options.
Eventually, though not implemented in any browser that I've been able to see, we'll be able to set the SVG background using the CSS background-image attribute. This just adds to the intriguing possibilities. update This functionality is implemented with Opera 9.5, as demonstrated in this example.
*Bonus material: a detailed instruction video from Nortel on the differences between raster and vector graphics. This is an older video, though. Support for SVG has increased, both with editing tools and with browsers. Other video formats and image lessons from the Nortel LearniT page.
Update I'm just playing around with this pattern, I'm aware that not all browsers are processing it correctly. This gave me a chance to do a little browser testing and also have a little fun with color. We've had so much cold and snow that I was desperate for a little color.
