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WHAT ARE VECTOR GRAPHICS?

Anyone who works with digital printing must know not only how to operate digital devices but also how to prepare files for output. With so many graphics file formats, it’s helpful to know the purpose of different file formats and the applications that create them. In this article, we will explore vector graphics in Adobe Illustrator for Mac and Windows (www.adobe.com/illustrator). CorelDRAW is a similar program for Windows only (www.corel.com).

Vector graphics are based on mathematical descriptions of points, lines and curves. This means they are resolution-independent and can be scaled to any size without losing quality. Since they have no resolution until printed, the final value depends on the output device used. The first vector-graphics drawing program, Adobe Illustrator, was introduced in 1986. It was based on font development software and the PostScript file format. Originally designed for Macs, it is also available for Windows. CorelDRAW was originally developed by Microsoft Windows and was initially released in 1989. Both programs are used for drawings, diagrams, logos and type.

Vector graphic programs such as Adobe Illustrator and CorelDRAW allow you to create and edit vector graphics. A combination of points, lines and curves are used to create shapes and graphic illustrations that are based on a mathematical formula. These vector graphic programs are most ideal for logos and diagrams that do not require a lot of detail. Advantages of vector graphics include being scalable and having smaller file sizes compared to raster images, which makes it appropriate for sign printing.

GETTING STARTED

How to draw. Illustrator has many tools for drawing vector graphics: the Line Segment Tool, the Rectangle Tool, the Pencil Tool, and the Pen Tool (see Figure 1).

Figure 1. Tools in Illustrator

Strokes and fills. A stroke is a visible outline of an object or path. You can change both the width and the color of the stroke could be in Illustrator. In addition, dashed strokes can be created using Path Options while stylized strokes can be created using brushes.

A fill is a color, gradient or pattern inside of an object. Both strokes and fills can be configured right on the toolbar. The stroke color is set in blue and the fill color is set in red.

Colors, Swatches and Patterns. Colors in Illustrator are available in CMYK or RGB modes. In a printing environment, the CMYK mode is usually used as opposed to the RGB mode. Select a specific color for your stroke or fill can be done using the Color Picker (see Figure 2). The color can be chosen based on HSB, RGB, CMYK, or Hexadecimal values.

Swatches are colors, tints, gradient and patterns that are named. Swatches can appear individually as well as in groups. Libraries of swatches from other documents can also be chosen in the Swatches panel.

There are two types of patterns that exist in Illustrator: fill patterns and brush patterns. Fill patterns are used for filling objects, while brush patterns are used to outline objects. Illustrator does come with a number of default patterns for you to use, but customized patterns can also be created.

To draw a curve in Illustrator, click-and-drag the Pen Tool to draw Bezier curve points out of the anchor points.
Figure 2: Use the Color Picker to select colors in RGB, CMYK, HSB, or hexadecimal values.

Tracing. Use tracing when you want to make a new drawing from a photo. Tracing is used to convert raster images into vector graphics, gaining the vector’s resolution independence and small file size, and also artistic effects (see Figure 3). There are two ways to trace images: automatically and manually.

Automatic tracing is the fastest way to turn bitmapped into vector artwork. First, open the source image that you want Illustrator to trace automatically. Once the image is opened, simply select Object > Live Trace > Make. The program will automatically produce a vector graphic based on the source image.

Manual tracing artwork is easy with Illustrator’s template layers. First, place the image you want to trace (File > Place, then select the Template option) in a new template layer. Then, trace it manually using the Pen Tool or Pencil Tool.

Figure 3: Tracing is useful to create a vector graphic from a scan or digital photo, gaining the vector graphic’s advantage of scalability and small file size. In these two illustrations, a digital photo of a Chinese paper cut (left) has been traced in Illustrator using the Autotrace tool (right).

Spot colors are color inks that are made from unique pigments or dyes, many of which are outside the gamut of four-color process printing. In digital publishing applications, spot means that the color will be transmitted to the print file as a named color, such as “Pantone Orange 021 C.” When printed as separations, named colors will come out on separate printing plates.

The Pantone Matching System (see Figure 4) is one of the most widely recognized spot-color systems. The system includes several swatch books printed on coated, uncoated and matte paper, including solid, process, metallic and pastel colors. Pantone solid colors are based on 14 primary-color inks that are mixed to form over 1,400 colors specified in the swatch books.

Figure 4: The Pantone Matching System is one of the most widely recognized spot-color specification systems. For lithographic printing, colors are mixed from 14 primary-color inks and often are outside the gamut of CMYK printers.

A CMYK printing process has a much smaller gamut than Pantone. As spot colors are made from unique pigments and dyes, they cannot be matched exactly on press or proofer in CMYK.

Although it is sometimes difficult to simulate spot color on press and printer, an inkjet printer has a larger gamut than a press. Therefore, when using an inkjet printer to proof for a printing press, the inkjet may be able to match more spot colors than the press.

GETTING COLOR RIGHT

If you draw in an illustration program, you’ll create color with reference to the computer screen. How can you be sure the color you see on-screen will be the same color you print? The best way is to set up the program’s color management workflow (see Figure 5) and create color profiles. For most accurate results, you’ll need to set up a printer profile and a monitor profile as in the following steps:

In the Edit > Color Setup dialog box, select a standard working space. The most common are the small-gamut sRGB for home computers, and the larger-gamut Adobe RGB for professional graphics. Don’t use your monitor profile for the standard working space, as it should be a “standard” profile that anyone can get.

If you have a color measurement device and application for monitor profiling, calibrate and profile your monitor. The application will read the standard monitor profile directly from the display settings.

Figure 5: To get color to come out right, specify a standard working space (smaller sRGB or larger Adobe RGB, left), and install and select your printer (right) profile for output or for soft-proofing.

Load your printer profile into the Profiles folder (for Mac: Library > Color > ColorSync Profiles; for Windows: WINNT > System > System 32 > Spool > Drivers > Color). In the Print dialog box, select your printer’s ICC profile as the Printer Profile.

To see how color will look when printed, use the View > Proof Setup dialog box. Select Custom and choose your printer profile as the output device.

Getting an exact color match is almost impossible because computer monitors display color in RGB, which as a huge color range, while printers use a smaller, four-color CMYK gamut. However, by profiling your printer and monitor you will be able to produce consistent, predictable color.

Click here to read Part 1 of this article series.

Click here to read Part 3 of this article series.