Chances are, if you have assets like logos to put on a Web page then the original file will be be some sort of Postscript, from a Postscript generating program such as Quark XPress or Adobe Illustrator. While Postscript is fine for print jobs it poses special problems to the screen-oriented designer.
Postscript is one of the most elegant and powerful pieces of software ever developed. It's a much over-used word in this industry, but PostScript really did revolutionise printing, and the way people think about output.
Trouble is, in revolutionising print it spawned an entire generation of software tools that took the way PostScript regards the world - as smooth vectors - as gospel.
In a screen-oriented age, like the one that the Web is creating, having smooth curves and the ability to print on all sorts of printers is less important than legibility. PostScript is vector-based, the Web is bitmapped.
Lately things have been improving: Photoshop, of course, has useful tools for dealing with small images; Freehand, notably, has the ability to export its vector artwork as nicely anti-aliased PICTs.
However to get a PostScript file to render nicely for the Web still means knowing a little voodoo, and having the right tools to hand.
For example, instead of there being a nice conistent format for PostScript files we have these ugly things called EPSs to deal with. An EPS is a lump of PostScript drawing code, together with bitmaps and information of things like the fonts used to create it.
Any program worth its PostScript salt can place an EPS file inside another document, so you would have thought the task of creating a screen rasterised, neat graphics file would be simple: just open an EPS in a bitmap oriented program like Photoshop.
Unfortunately, not so. Being able to place an EPS file in a document is not the same as actually decoding the Postscript in that document. Place just means being able to stick the data in a document without worrying about what kind of Postscript it is, and leave it to the printer to sort out.
There are as many different interpretations of Postscript as there are Postscript-creating programs, and only the very foolish would attempt to write a way to import them all. Instead most programs rely on an embedded preview in the EPS file - PICT on the Mac, TIFF on the PC - to display what the file should look like.
Sometimes these previews are horrible low resolution things, sometimes there are actually quite good - but not perfect. If you've ever tried to open a Quark EPS in Photoshop you'll know what I mean. Photoshop appears to load the EPS without a quibble and at first glance everthing looks fine: it's only when you zoom in a little that you realise that your image is hopelessly jagged.
Here's the archetypal jagged preview. It's ok-ish at 100per cent, until you notice how weird the diagonals and curves look...
