Saving an EPS image

When preparing an image for placement inside a drawing or page-layout document that will be printed to a PostScript output device, many artists prefer to save the image in the EPS format. Converting the image to PostScript up front prevents the drawing or page-layout program from doing the work. The result is an image that prints more quickly and with less chance of problems. (Note that an image does not look any different when saved in EPS. The idea that the EPS format somehow blesses an image with better resolution is pure nonsense.)

A second point in the EPS format's favor is clipping paths. As explained graphically at the end of Chapter 8, a clipping path defines a free-form boundary around an image. When you place the image into an object-oriented program, everything outside the clipping path becomes transparent. While some programs — notably InDesign and PageMaker — recognize clipping paths saved with a TIFF image, many programs acknowledge a clipping path only when saved in the EPS format.

Third, although Illustrator has remedied the problems it had importing TIFF images, it still likes EPS best, especially where screen display is concerned. Thanks to the EPS file's fixed preview, Illustrator can display an EPS image on screen very quickly compared with other file formats. And Illustrator can display an EPS image both in the preview mode and in the super-fast artwork mode.

So if you want to import an image into Illustrator, QuarkXPress, or another object-oriented program, your best bet is EPS. On the downside, EPS is an inefficient format for saving images thanks to the laborious way that it describes pixels. An EPS image may be three to four times larger than the same image saved to the TIFF format with LZW compression. But this is the price we pay for reliable printing.

Caution Absolutely avoid the EPS format if you plan on printing your final pages to a non-PostScript printer. This defeats the entire purpose of EPS, which is meant to avoid printing problems, not cause them. When printing without PostScript, use TIFF or JPEG.

To save an image in the EPS format, choose Photoshop EPS from the Format pop-up menu in the Save dialog box. After you press Enter, Photoshop displays the dialog box shown in Figure 3-11. The options in this dialog box work as follows:

♦ Preview: Technically, an EPS document comprises two parts: a pure PostScript-language description of the graphic for the printer and a bitmapped preview so you can see the graphic on screen. Select the TIFF (8 bits/pixel) option from the Preview pop-up menu to save a 256-color TIFF preview of the image. The 1-bit option provides a black-and-white preview only, which is useful if you want to save a little room on disk. Select None to include no preview and save even more disk space.

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Figure 3-11: When you save an image in the EPS format, you can specify the type of preview and tack on some printing attributes.

♦ Encoding: If you're saving an image for import into Illustrator, QuarkXPress, or some other established program, select the Binary encoding option (also known as Huffman encoding), which compresses an EPS document by substituting shorter codes for frequently used characters. The letter a, for example, receives the 3-bit code 010, rather than its standard 8-bit ASCII code, 01100001 (the binary equivalent of what we humans call 97).

Sadly, some programs and printers don't recognize Huffman encoding, in which case you must select the less efficient ASCII option. ASCII stands for American Standard Code for Information Interchange, which is fancy jargon for text-only. In other words, you can open and edit an ASCII EPS document in a word processor, provided you know how to read and write PostScript.

Actually, this can be a useful technique if you have a Mac file that won't open, especially if the file was sent to you electronically. Chances are that a Mac-specific header got into the works. Open the file in a word processor and look at the beginning. You should see the four characters %!PS. Anything that comes before this line is the Macintosh header. Delete the garbage before %!PS, save the file in text format, and try again to open the file in Photoshop.

The remaining Encoding options are JPEG settings. JPEG compression not only results in smaller files on disk but also degrades the quality of the image. Select JPEG (Maximum Quality) to invoke the least degradation. Better yet, avoid the JPEG settings altogether. These options work only if you plan to print your final artwork to a PostScript Level 2 or Level 3 device. Earlier PostScript printers do not support EPS artwork with JPEG compression and will choke on the code.

So to recap, ASCII results in really big files that work with virtually any printer or application. Binary creates smaller files that work with most mainstream applications but may choke some older-model printers. And the JPEG settings are compatible exclusively with Level 2 and later PostScript printers.

♦ Include Halftone Screen: Another advantage of EPS over other formats is that it can retain printing attributes. If you specified a custom halftone screen using the Screens button inside the Page Setup dialog box, you can save this setting with the EPS document by selecting the Include Halftone Screen check box. But be careful — you can just as easily ruin your image as help it. Read Chapter 18 before you select this check box.

♦ Include Transfer Function: As described in Chapter 18, you can change the brightness and contrast of a printed image using the Transfer button inside the Page Setup dialog box. To save these settings with the EPS document, select the Include Transfer Function check box. Again, this option can be dangerous when used casually. See Chapter 18 for more details.

♦ PostScript Color Management: Like JPEG compression, this check box is compatible with Level 2 and 3 printers only. It embeds a color profile, which helps the printer to massage the image during the printing cycle to generate more accurate colors. Unless you plan on printing to a Level 2 or later device, leave the option off. (For more information about color profiles, read Chapter 16.)

♦ Include Vector Data: Select this option if your file contains vector objects, including shapes, non-bitmap type, and layer clipping paths. Otherwise, Photoshop rasterizes the objects during the save process. When you select the option, Photoshop displays a warning in the dialog box to remind you that if you reopen the file in Photoshop, you rasterize any vector objects that you saved with the file.

♦ Transparent Whites: When saving black-and-white EPS images in Photoshop, the four check boxes previously discussed drop away, replaced by Transparent Whites. Select this option to make all white pixels in the image transparent.

Although Photoshop EPS is the only format that offers the Transparent Whites option, many programs — including Illustrator and InDesign — treat white pixels in black-and-white TIFF images as transparent as well.

♦ Image Interpolation: Turn on this option if you want another program to be able to interpolate the image when resampling it to another size. For example, suppose you import an EPS image into InDesign and scale it to 400 percent. If Image Interpolation is turned off, then InDesign just makes pixels in the image four times larger, as if you had used the nearest neighbor interpolation inside Photoshop. If you turn Image Interpolation on, however, InDesign applies bicubic interpolation in order to generate new pixels. (For details on nearest neighbor and bicubic interpolation, see the "General Preferences" section in Chapter 2.) Unless you have a reason for doing otherwise, turn this option on.

Learn Photoshop Now

Learn Photoshop Now

This first volume will guide you through the basics of Photoshop. Well start at the beginning and slowly be working our way through to the more advanced stuff but dont worry its all aimed at the total newbie.

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