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Printbuyers ONLINE-April 26 2004
Rasters, Vectors, and RIPs Made Simple - Part Two of a Two Part Article
After learning about raster files in part one of this article, everyone is most likely breathlessly anticipating vector files in part 2. Prepare to steady your hearts as you learn all about vector files.

Part Two-Vector Files
In part one, we learned that raster files are created with a specific number of dots. Each of which can be different and addressed and altered. This is perfect for smoothly blending photograph tones and the magic of raster-editing applications like Adobe Photoshop. But it is a nightmare for typography. In fact, if we turn back the clock a little more than 20 years to when there were only raster images, desktop publishing did not exist.

Those of us that remember the early days of personal computers can attest to the almost nonexistent freedom of on-screen font usage and sizing type. Moreover, printouts were done on some kind of mechanical device that resembled a typewriter or on a dot matrix printer. Font imaging onscreen and in print, as we know it today, was just about impossible. Based on what we learned last month, stop and think for a minute about the problems of type as a raster image. First, on-screen resolution is 72 DPI and print wants 300 DPI, which creates a major file size conflict. But it gets worse, since raster images lose resolution when enlarged. So, as I said, typography was a nightmare. Enter John Warnock and Chuck Geschke, two brilliant scientists who met and worked at Xerox’s Palo Alto Research Center (often referred to as Xerox PARC). Without getting into a complete history, these two men conceived the idea that made the desktop revolution possible and decided to form their own company. Behind Warnock’s home in Los Altos California was a creek called the Adobe creek, which seemed like a good name for a company; in 1982, Warnock and Geschke started Adobe Systems.

A year later, Adobe introduced PostScript, making the world of desktop publishing possible. The many contributions Adobe continues to make are staggering. But PostScript alone is an achievement that -- in my judgment -- may be second only to Gutenberg's.

Sound like an outlandish statement? Not if you think about it. The principal element of Gutenberg's innovation was his system of moveable type that enabled the key element of printing, typography, to become a standardized manufacturing reality. The printer could now efficiently set type to place in his printing press.

In effect, PostScript did the same for computer-generated typography. The device-independent mathematical outlines that enabled type to be produced easily and sharply at any size was a revolution over device-dependent (raster), bitmapped type. But PostScript did so much more to make desktop publishing happen; now a single software language could replace the need for a myriad of drivers and could put text and graphics on the same page at the same time.

Allow me to simplify all this for you while giving you a look at how vector files work. Instead of creating a file with a specific number of dots, suppose you define the perimeters and fill it with whatever number of dots are needed. Let’s take the letter T, for example. The perimeters, or outlines of the letter T are defined mathematically by vectors, hence the name vector file. These vectors are scalable meaning they can be enlarged or reduced and still easily describe the parameters of bigger or smaller areas. They can be filled with 72 DPI, 300 DPI, or 3000 DPI -- in effect, whatever is needed. Thus you now have scalable vectors that can be enlarged, used on-screen, or printed without any worries about resolution.

However, the dots that fill in between the vectors are all the same, which is no problem for most type. But it is a problem for photographs where tonality is needed. (Yes, I know you have seen vector clip art that is scalable and does seem to have some tonality.) The limitation of having the same dots between vectors is somewhat mitigated by placing vectors ever closer together, which gives the appearance of colors blending. In fact, Adobe later developed Adobe Illustrator, a drawing program using vectors. The latest version of this program does an amazing job of squeezing vectors closer and closer together, thereby producing amazing color blends. But it still doesn’t match raster images.

In order to print, vector graphics must be converted to raster images. This is the job of the RIP or Raster Image Processor. All vector and raster images go through the RIP, which converts vector graphics into raster images at the resolution needed for the printer. At one time, the only RIP was a PostScript RIP, which is still currently regarded as the best RIP. In a PostScript RIP the vectors are turned to rasters, all the elements of the page are placed, and the page is described in terms that the output device understands, usually in a series of on-off commands for each color. For example, it can tell an ink jet printer to squirt or not squirt a particular color or a platemaker when to turn a laser on or off.

Soon after the development of PostScript and scalable vector graphics, Adobe proceeded to get the rights to start digitizing or vectoring fonts. The fonts they produce, known as PostScript or Type 1 fonts, are still regarded by graphic designers today as the best fonts. However, because Microsoft and Apple didn’t want to be restricted to Adobe fonts, they developed their own fonts, called True Type. These are the fonts that come with new PCs and are relatively inexpensive when compared to the superior Type 1 fonts. Today Adobe, Microsoft, Apple, and all other producers are cooperating on a new font called Open Type.

Since all print projects had to be RIP’ed, inkjet printer manufacturers like HP didn’t want to pay the royalties for Adobe PostScript and developed their own RIPs. Today Adobe PostScript used for PostScript RIPs has decreased dramatically in price and is available from many inkjet and laser printer manufacturers. A PostScript RIP usually produces superior results and is well worth the extra money for better graphics. Adobe sells PostScript to RIP manufacturers. Many commercial printers use RIPs with Adobe PostScript, which are still highly regarded. However, there are RIPS that use what is commonly referred to as clones that also produce good results.

So there you have it. Now you are an expert on rasters, vectors, and RIPS. You also should have a better perspective on the monster contribution Adobe has made to this industry and continues to make with PDF and the PDF/JDF workflow that will soon become critical for the automation of our industry.

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