Photoshop 6 for Windows Bible- P5

Photoshop 6 for Windows Bible- P5:If you are reading this foreword, it probably means that you’ve purchased a copyof Adobe Photoshop 6.0, and for that I and the rest of the Photoshop team atAdobe thank you.If you own a previous edition of the Photoshop Bible, you probably know what toexpect. If not, then get ready for an interesting trip.
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Photoshop 6 for Windows Bible- P5 Chapter 3 ✦ Image Fundamentals 85 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. Tip 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.Cross- One exception: If you’re creating a grayscale image for use with Filter ➪ Distort ➪Reference 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.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. Cross- Notice that I lump Web standards GIF and PNG in with the special-purpose formats. Reference 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. Note ...