85 Chapter 3 ✦ Image Fundamentals File formats represent different ways to save a file to disk. Some formats provide unique image-compression schemes, which save an image in a manner that consumes less space on disk. Other formats enable Photoshop to trade images with different applications running under Windows or some other platform. The native format Like most programs, Photoshop offers its own native format — that is, a format optimized for Photoshop’s particular capabilities and functions. This .psd format saves every attribute that you can apply in Photoshop — including layers, extra channels, file info, and so on — and is compatible with Versions 3 and later of the program. Of course, when you open files in earlier versions of Photoshop, you lose file attributes related to Version 6 features, such as annotations, color proof options, and so on. Perhaps not surprisingly, Photoshop can open and save more quickly in its native format than in any other format. The native format also offers image compression. Like TIFF’s compression, the Photoshop compression scheme does not result in any loss of data. But Photoshop can compress and decompress its native format much more quickly than TIFF, and the compression scheme is better able to minimize the size of mask channels (as explained in Chapter 9). The downside of the Photoshop format is that relatively few applications other than Photoshop support it, and those that do don’t always do a great job. Some applications such as CorelPhoto-Paint and Adobe After Effects can open a layered Photoshop image and interpret each layer independently. But most of the others limit their support to flat Photoshop files. To accommodate these programs, you can either (1) deselect the Layers check box in the Save dialog box to save a flat- tened version of the image or (2) activate the Maximize Backward Compatibility check box in the Preferences dialog box. However, I intensely dislike both of these options. (In fact, you should be sure to turn off File Compatibility, for reasons explained in Chapter 2.) The native .psd format was never intended to function as an interapplication standard; it was meant for Photoshop alone. So use it that way. If you want to trade a flattened image with some other program, use TIFF, JPEG, or one of the other universal formats explained over the course of this chapter. One exception: If you’re creating a grayscale image for use with Filter ➪ Distort ➪ Displace, you have to create a Photoshop 2.0–compatible file. The best bet is to save the image in the Photoshop 2.0 format. Otherwise the Displace filter won’t see the grayscale image. I tell you more about this filter in Chapter A on the CD-ROM that accompanies this book. Cross- Reference Tip 86 Part I ✦ Welcome to Photoshop 6 Special-purpose formats With 20 file formats to choose from, you can imagine that most are not the kinds you’ll be using on a regular basis. In fact, apart from the native Photoshop format, you’ll probably want to stick with TIFF, JPEG, and GIF for Web images and EPS when preparing images for placement into QuarkXPress, PageMaker, and others. Many of the other formats are provided simply so you can open an image created on another platform, saved from some antiquated paint program, or downloaded from the Web. In the spirit of sweeping away the chaff so we can move on to the good stuff, I cover these special-purpose formats first. Notice that I lump Web standards GIF and PNG in with the special-purpose formats. The reason is simple— if you don’t design for the Web, you rarely need them. On the other hand, if you do design for the Web, the formats take on special significance, which is why I cover them in depth in Chapter 19. Microsoft Paint’s BMP BMP (Windows Bitmap) is the native format for Microsoft Paint (included with Windows) and is supported by a variety of Windows and DOS applications. Photoshop supports BMP images with up to 16 million colors. You also can use RLE (Run-Length Encoding), a lossless compression scheme specifically applicable to the BMP format. The term lossless refers to compression schemes that conserve space on disk without sacrificing any data in the image, such as BMP’s RLE and TIFF’s LZW (Lempel-Ziv-Welch). The only reasons not to use lossless compression are that it slows down the open and save operations and it may prevent less-sophisticated applications from opening an image. (Lossy compression routines, such as JPEG, sacrifice a user-defined amount of data to conserve even more disk space, as I explain later.) The most common use for BMP is to create images for use in help files and Windows wallpaper. In fact, rolling your own wallpaper is a fun way to show off your Photoshop skills, which is exactly what I did in Color Plate 3-1. For the best results, make sure you set your image to exactly the same pixel dimensions as your screen (which you can check from the Settings panel in the Display control panel). To conserve memory, you may want to reduce the number of colors in your wallpa- per image to 256 using Image ➪ Mode ➪ Indexed Color. Although Color Plate 3-1 may look quite colorful, I did in fact reduce the palette to a bare-bones 256 colors. See Chapter 19 for the complete lowdown on indexed color. When you save the wallpaper image, Photoshop displays the options shown in Figure 3-8. Generally, you’ll want to select the Windows and Compress (RLE) options, but it really doesn’t matter when creating wallpaper. Don’t mess with the Depth options. Either you reduced the bit depth using the Indexed Color command as I directed previously or you didn’t. There’s no sense in changing the colors during the save process. Note Cross- Reference 87 Chapter 3 ✦ Image Fundamentals Figure 3-8: Select the options shown here when saving a BMP image for use as a desktop background. Leave the Depth setting alone. To load the wallpaper onto your desktop, right-click anywhere on the desktop and choose the Properties command. This brings up the Display Properties dialog box shown in Figure 3-9. Click the Browse button and locate your BMP image on disk. Then click the apply button to see how it looks. CompuServe’s GIF In the old days, the CompuServe online service championed GIF (short for Graphics Interchange Format) as a means of compressing files so you could quickly transfer photographs over your modem. Like TIFF, GIF uses LZW compression, but unlike TIFF, GIF is limited to just 256 colors. With the advent of the World Wide Web, the GIF format has grown slightly more sophisticated. Two varieties of GIF currently exist, known by the helpful codes 87a and 89a. GIF87a supports strictly opaque pixels; GIF89a permits some pixels to be transparent. To open either kind of image, choose File ➪ Open. 88 Part I ✦ Welcome to Photoshop 6 Figure 3-9: You can load a BMP file as desktop wallpaper using the Display Properties control panel provided with Windows 95 and later. You can save an image with or without transparency by choosing File ➪ Save and selecting CompuServe GIF from the Format pop-up menu. When you index (reduce) the image to 256 colors — which you can do either before or during the file save process— select the Transparency check box in the Indexed Color dialog box if you want any areas of the image that are transparent to remain transparent when you view the image file in a Web browser. Chapter 19 explores this and other issues related to GIF transparency in detail. If you’re resistant to change and want to create GIFs with transparency via the old Export ➪ GIF89A command, you can; Adobe includes the command as an optional plug-in on the program CD just for old fogeys like you. But you’ll save yourself time and trouble if you get acquainted with the new method: PC Paintbrush’s PCX PCX doesn’t stand for anything. Rather, it’s the extension PC Paintbrush assigns to images saved in its native file format. Although the format is losing favor, many PCX images are still in use today, largely because PC Paintbrush is the oldest painting 6 Photoshop 6 89 Chapter 3 ✦ Image Fundamentals program for DOS. Photoshop supports PCX images with up to 16 million colors. You can find an enormous amount of art, usually clip art, in this format. However, don’t save files to PCX unless a client specifically demands it. Other formats are better. Adobe’s paperless PDF The Portable Document Format (PDF) is a variation on the PostScript printing language that enables you to view electronically produced documents on screen. This means you can create a publication in QuarkXPress or PageMaker, export it to PDF, and distribute it without worrying about color separations, binding, and other printing costs. Using a program called Adobe Acrobat, you can open PDF doc- uments, zoom in and out of them, and follow hypertext links by clicking highlighted words. Adobe distributes Mac, Windows, and UNIX versions of the Acrobat Reader for free, so almost anyone with a computer can view your stuff in full, natural color. PDF files come in two flavors: those that contain just a single image and those that contain multiple pages and images. Photoshop can save only single-image PDF files, but it can open multipage files. The program rasterizes both types of files when it opens them. You open PDF files in different ways depending on what elements of the file you want to access: ✦ Use File ➪ Open to open a particular page in a multipage PDF file. After select- ing the page you want to view, you can set the image size and resolution of the rasterized file. You also can choose File ➪ Place to add a page as a new layer to an open image; in this case, you can’t control size and resolution before adding the page. However, you can scale the page after the fact as you can any layer. ✦ Select Import ➪ PDF Image to bring up a dialog box that enables you to open a particular image in the PDF file. ✦ Choose Automate ➪ Multi-Page PDF to PSD to turn each page in the PDF file into a separate Photoshop image file. The real question, however, is why would you want to open or place a PDF file in Photoshop instead of viewing it in Acrobat, which provides you with a full range of document viewing tools not found in Photoshop? Furthermore, because you can save only single-page PDF files, why on earth would you save to PDF in Photoshop? I can think of two scenarios where Photoshop’s PDF functions may come in handy: ✦ You want to see how images in a PDF document will look when printed on a high-resolution printer. Open the PDF file using File➪ Open, set the resolution to match that of the output device, and eyeball those images on-screen. This “soft-proofing” technique enables you to spot defects that may not be notice- able in draft proofs that you output on a low-res printer. 90 Part I ✦ Welcome to Photoshop 6 ✦ You need a convenient way to distribute images for approval or input. You can save an image as a PDF file and send it to clients and colleagues, who can view the image in Acrobat if they don’t have Photoshop. In Photoshop 6, you can even add text or voice annotations to your PDF file. In addition to annotations, Photoshop PDF supports layers, transparency, embedded color profiles, spot colors, duotones, and more. This enables you to route an image for approval without having to flatten the image or otherwise strip it of its Photoshop 6 features. Of course, features not supported by Acrobat aren’t accessible to the viewer. When you save to PDF in Photoshop, you have a choice of two encoding options. Choose ZIP only for images that feature large expanses of a single color; otherwise, opt for JPEG. Keep the Quality option set to Maximum to maintain the best print quality, just as you do for regular JPEG files. Select the Include Vector Data and Embed Fonts check boxes to retain any vector graphics and font data, respectively. Alternatively, you can select the Use Outlines for Text to save text as character out- lines that are editable in the PDF file. The final option, Image Interpolation, enables other programs to interpolate the image when resampling to another size. If you select JPEG encoding, you need a PostScript Level 2 or later printer to output your PDF file. Also be aware that separating files into individual plates can be problematic. Apple’s PICT PICT (Macintosh Picture) is the Macintosh system software’s native graphics format. Based on the QuickDraw display language that the system software uses to convey images on screen, PICT handles object-oriented artwork and bitmapped images with equal aplomb. It supports images in any bit depth, size, or resolution. PICT even supports 32-bit images, so you can save a fourth masking channel when working in the RGB mode. PICT is obviously popular with the Macintosh crowd, especially folks who don’t know much about graphics. So if you share a lot of files with Mac-type people, you may occasionally be asked to supply images in the PICT format. If you’re trying to save an image in a format that your mom can open on her Mac, for example, PICT may be a better choice than JPEG. Heck, you can open PICT files inside a word processor, including everything from SimpleText to Microsoft Word. Just be sure mom has QuickTime loaded on her machine. When you save a PICT image, Photoshop lets you set the bit depth. You should always stick with the default option, which is the highest setting available for the particular image. Don’t mess around with these options; they apply automatic pattern dithering, which is a bad thing. Note 6 Photoshop 6 91 Chapter 3 ✦ Image Fundamentals On the flip side, you may need to open a PICT file a Mac friend sends you. Photoshop can do this, but one problem may trip you up: On the Mac, you have the option of saving PICT files with a variety of JPEG compressions supplied by Apple’s QuickTime. Unless you have QuickTime installed on your PC—which you might if you do a lot of surfing on the Web —you won’t be able to open compressed PICT images. Pixar workstations Pixar has created some of the most memorable computer-animated movies and commercials in recent memory. Examples include the desk lamps playing with a beach ball from Luxo, Jr., the run-amok toddler from the Oscar-winning Tin Toy, and the commercial adventures of a Listerine bottle that boxes gingivitis one day and swings Tarzan-like through a spearmint forest the next. But Pixar really made the grade with the feature-length Toy Story, which provided Disney with enough merchandising options to last a lifetime. Pixar works its 3D magic using mondo-expensive workstations. Photoshop enables you to open a still image created on a Pixar machine or to save an image to the Pixar format so you can integrate it into a 3D rendering. The Pixar format supports gray- scale and RGB images. PNG for the Web Pronounced ping, the PNG format enables you to save 16 million color images with- out compression for use on the Web. As I write this, neither Netscape Navigator nor Microsoft Internet Explorer support PNG without the help of a special plug-in. But for those folks who want full-color images without the pesky visual compression artifacts you get with JPEG, PNG may well be a big player in the future. (Of course, I wrote this same paragraph two years ago, so there’s always the chance PNG will never gain acceptance.) PNG was invented for the Web and I’ve never seen anyone use it for a purpose other than the Web. Find more information about PNG in Chapter 19, which covers Web issues in detail. Scitex image-processors Some high-end commercial printers use Scitex printing devices to generate color separations of images and other documents. Photoshop can open images digitized with Scitex scanners and save the edited images to the Scitex CT (Continuous Tone) format. Because you need special hardware to transfer images from the PC to a Scitex drive, you’ll probably want to consult with your local Scitex service bureau technician before saving to the CT format. The technician may prefer that you submit images in the native Photoshop, TIFF, or JPEG format. The Scitex CT format supports grayscale, RGB, and CMYK images. Cross- Reference 92 Part I ✦ Welcome to Photoshop 6 TrueVision’s TGA TrueVision’s Targa and NuVista video boards enable you to overlay computer graphics and animation onto live video. The effect is called chroma keying because, typically, a key color is set aside to let the live video show through. TrueVision designed the TGA (Targa) format to support 32-bit images that include 8-bit alpha channels capable of displaying the live video. Support for TGA is widely imple- mented among professional-level color and video applications on the PC. Interapplication formats In the name of interapplication harmony, Photoshop supports a few software- specific formats that permit you to trade files with popular object-oriented programs such as Illustrator and QuarkXPress. Every one of these formats is a variation on EPS (Encapsulated PostScript), which is based in turn on Adobe’s industry-standard PostScript printing language. You can use Photoshop to edit frames from a QuickTime movie created with Adobe Premiere. Rasterizing an Illustrator or FreeHand file Photoshop supports object-oriented files saved in the EPS format. EPS is specifically designed to save object-oriented graphics that you intend to print to a PostScript output device. Just about every drawing and page-layout program on the planet (and a few on Mars) can save EPS documents. Prior to Version 4, Photoshop could interpret only a small subset of EPS operations supported by Illustrator (including the native .ai format). But then Photoshop 4 came along and offered a full-blown EPS translation engine, capable of interpreting EPS illustrations created in FreeHand, CorelDraw, Deneba’s Canvas, and more. You can even open EPS drawings that contain imported images, something else Version 3 could not do. When you open an EPS or native Illustrator document, Photoshop rasterizes (or renders) the artwork — that is, it converts the artwork from a collection of objects to a bitmapped image. During the open operation, Photoshop presents the Rasterize Generic EPS Format dialog box (see Figure 3-10), which enables you to specify the size and resolution of the image, just as you can in the New dialog box. Assuming the illustration contains no imported images, you can render it as large or as small as you want without any loss of image quality. If the EPS illustration does contain an imported image or two, you need to know the resolution of the images and factor this information into the Rasterize Generic EPS Format dialog box. Select anything but Pixels from both the Width and Height pop- up menus, and leave the suggested values unchanged. Then enter the setting for the highest-resolution imported image into the Resolution option box. (If all the images are low-res, you may want to double or triple the Resolution value to ensure that the objects render smoothly.) Tip 93 Chapter 3 ✦ Image Fundamentals Figure 3-10: You can specify the size and resolution at which Photoshop renders an EPS illustration. You should always select the Anti-aliased check box unless you’re rendering a very large image — say, 300 ppi or higher. Antialiasing blurs pixels to soften the edges of the objects so they don’t appear jagged. When you’re rendering a very large image, the difference between image and printer resolution is less noticeable, so antialias- ing is unwarranted. Photoshop renders the illustration to a single layer against a transparent back- ground. Before you can save the rasterized image to a format other than native Photoshop, you must eliminate the transparency by choosing Layer➪ Flatten Image. Or save a flattened version of the image to a separate file by choosing the As a Copy option in the Save dialog box. Rendering an EPS illustration is an extremely useful technique for resolving print- ing problems. If you regularly work in Illustrator or FreeHand, you no doubt have encountered limitcheck errors, which occur when an illustration is too complex for an imagesetter or other high-end output device to print. If you’re frustrated with the printer and tired of wasting your evening trying to figure out what’s wrong (sound familiar?), use Photoshop to render the illustration at 300 ppi and print it. Nine times out of ten, this technique works flawlessly. If Photoshop can’t parse the EPS file—a techy way of saying Photoshop can’t break down the individual objects — it attempts to open the PICT (Mac) or TIFF (Windows) preview. This exercise is usually futile, but occasionally you may wish to take a quick look at an illustration to, say, match the placement of elements in an image to those in the drawing. Placing an EPS illustration If you want to introduce an EPS graphic into the foreground image rather than to render it into a new image window of its own, choose File➪ Place. Unlike other File menu commands, Place supports only EPS illustrations and PDF files. Tip 94 Part I ✦ Welcome to Photoshop 6 After you import the EPS graphic, it appears inside a box — which Photoshop calls a bounding box — with a great big X across it. You can move, scale, and rotate the illustration into position before rasterizing it to pixels. Drag a corner handle to resize the image; drag outside the image to rotate it. You can also nudge the graphic into position by pressing the arrow keys. When everything is the way you want it, press Enter or double-click inside the box to rasterize the illustration. If the place- ment isn’t perfect, not to worry. The graphic appears on a separate layer, so you can move it with complete freedom. To cancel the Place operation, press Escape instead of Enter. 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 for- mat 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. 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. Caution [...]... printer, select the final option Be forewarned, however, that the composite image significantly increases the size of the master document on disk 97 98 Part I ✦ Welcome to Photoshop 6 Photoshop Figure 3-12: The extra options for the DCS 1.0 format (top) and those for the DCS 2.0 format (bottom) 6 Notice the two new options at the bottom of the options dialog boxes for DCS 1.0 and 2.0: Include Vector... fact, TIFF is the only format other than DCS 2.0, “raw,” and the native Photoshop format that can save more than four channels To save a TIFF file without extra mask channels, deselect the Alpha check box in the Save dialog box (For an introduction to channels, read Chapter 16. ) Photoshop Chapter 3 ✦ Image Fundamentals 6 Even more impressive, TIFF supports multiple layers in Photoshop 6 If you want layers... strongly advises against using it to edit Photoshop 6 TIFF files The oddball formats Can you believe it? After plowing through a half-million formats, I still haven’t covered them all The last three are the odd men out One format has a purpose so specific that Photoshop can open files saved in the format but it can’t save to the format The second is a new format that, while moderately promising, is... computers may contain 16 109 110 Part I ✦ Welcome to Photoshop 6 Figure 3-18: Photoshop requires you to specify the size of an image and the number of color channels when you open an image that does not conform to a standardized file format ✦ Byte Order: If you specify 16 bits per channel, you must tell Photoshop whether the image comes from a Mac or a PC ✦ Header: This value tells Photoshop how many bytes... best format converter bar none, DeBabelizer handles every format Photoshop handles, as well as Dr Halo’s CUT, Fractal Design Painter’s RIFF, the animation formats PICS, FLI, and ANM, as well as UNIX workstation formats for Silicon Graphics, Sun Microsystems, and others Photoshop Still out of it? Go online and check out such forums as ADOBEAPPS on CompuServe The Usenet newsgroups comp.graphics.apps .photoshop. .. nice, sharp edges 105 1 06 Part I ✦ Welcome to Photoshop 6 Figure 3- 16: Photoshop 6 offers a choice of compression schemes for a TIFF file as well as the option to write the file as an image pyramid Note If names such as Huffman, LZW, and ZIP ring a faint bell, it may be because these are the same compression schemes used by PKzip, WinZIP, and other file compression utilities For this reason, using an... Save dialog box (See the earlier section “Choosing other save options” for a look at all the new controls in the dialog box.) Photoshop When you save an image as a TIFF file, Photoshop displays the TIFF Options dialog box (see Figure 3- 16) , which offers expanded controls in Version 6: 6 ✦ Compression: Formerly, you could apply only one form of compression to TIFF files — LZW (Lempel-Ziv-Welch) compression... this book’s CD-ROM Taping notes to your image 6 Photoshop 6 enables you to slap the digital equivalent of a sticky note onto your image The notes can be viewed in Adobe Acrobat (assuming that you save the image in the PDF format) as well as in Photoshop 6 You can jot down ideas that you want to remember later, for example Or, if you’re routing an image for approval, you can ask questions about a certain... Photoshop also enables you to save to the raw document format This capability is useful when you create files you want to transfer to mainframe systems or output to devices that don’t support other formats, such as the Kodak XL7700 Chapter 3 ✦ Image Fundamentals Caution Do not save 2 56- color indexed images to the raw format or you will lose the color lookup table and, therefore, lose all color information... someone may have an answer for you Adding file information and annotations 6 On top of pixels, alpha channels, color profiles, and all the other image data you can cram into your image files, you can add a variety of reference information — where you shot the picture, who owns the image copyright, and so on In Version 6, this extra data can take the form of cataloging information that you enter in . Photoshop to trade images with different applications running under Windows or some other platform. The native format Like most programs, Photoshop offers its own native format — that is, a format. final option. Be forewarned, however, that the composite image significantly increases the size of the master docu- ment on disk. 6 Photoshop 6 98 Part I ✦ Welcome to Photoshop 6 Figure 3-12: The. the CD-ROM that accompanies this book. Cross- Reference Tip 86 Part I ✦ Welcome to Photoshop 6 Special-purpose formats With 20 file formats to choose from, you can imagine that most are not the