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website design tips » September 2004: “ ‘Vector & Raster’ Are Not A Type Of Dinosaur”
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CORE BT Application Graphical User Interface (GUI) and Advanced CSS Design. Requirements included outstanding design and flexible advanced XHTML/CSS
web site design tips
This month’s website design tip is on the topic of vector vs. raster graphics.
web site design techniques
This month’s website design technique demonstrates a wacky way to fake a resizable background image in a DIV.
Rast, Raster, Rastest
.GIF and .JPG are special raster formats. They are compressed formats and should not be used until you are ready for the final stage of image processing. For example if you've been in Photoshop touching up a photo you should be saving that file as a PSD (Photoshop document) then when you are ready to put that image on, say, a web page, you save another version out as a JPG or GIF. Often, photos generally save out for the best as a JPG, and vector images as GIF, though that’s far from a hard and fast rule.
Every time you re-save a JPG (or GIF if you choose less colours than the original GIF) you re-compress it, lowering the quality. That’s why these file types are best when created from the source document. JPG and GIF are not very good files to use as original source images. One exception is that some JPGs are saved out with very slight compression, set to 100, which compresses the image just enough to bring the file size down to a more acceptable size but also does not ditch too much data. Another exception would be if your original has 256 or less colours, in which case the GIF format could save it out exactly as the original.
Here's a more detailed look at image types.