Taking Your Talent to the Web- P17 potx

Save the VisiBone swatch so it is always available when you work in Photoshop. Now pat yourself on the back. Many of your peers have no idea that this spe- cial swatch exists, that it comes bundled with Photoshop, and that it can greatly ease the creation of meaningful and attractive color schemes for the Web. You are ahead of the game. If you’re stuck using an older version of Photoshop or an alternative image editor, you can download the VisiBone palette free of charge at www.visibone.com. While there, help yourself to additional VisiBone palettes for other software programs you or your teammates use, includ- ing Adobe Illustrator and ImageReady, Macromedia Fireworks, Bare Bones BBEdit, Jasc Paint Shop Pro, Allaire HomeSite, MetaCreations Painter, or the GIMP (an image editor for Linux). You need it; they’ve got it. For additional wisdom on the Color Cube, see Lynda Weinman’s site at www.lynda.com and David Siegel’s at www.killersites.com. You also might want to buy Weinman’s Designing Web Graphics and Coloring Web Graph- ics, both of which are available from New Riders Press, and are pretty much the standard industry texts. They are full of practical examples and offer stimulating and innovative ideas from the earliest days of web design. Another standard industry text, David Siegel’s Creating Killer Websites, is also available from New Riders and also provides extensive information on the subjects we cover in this chapter. It’s a beautifully written book full of great ideas, but it is also a book of its time (1996), and many of the prac- tices it preaches would now be considered harmful to the development of a semantic Web based on W3C Recommendations. We own and cherish this book, which was greatly influential in our development, and we recom- mend it as long as you know which of its visual techniques to shun. (If you’re unsure, wait for the book’s third Edition…we hear it’s coming soon.) FORMAT THIS: GIFS, JPEGS, AND SUCH Raster images come in at least as many formats as there are software pro- grams and operating systems. On the Web, however, we tend to use two formats almost exclusively: GIF and JPEG. (As explained previously, ani- mated GIFs are a special instance of the GIF format.) 221 Taking Your Talent to the Web 13 0732 CH09 4/24/01 11:22 AM Page 221 PNG is yet another web format, one that has been little supported in the past. Some newer browsers have begun to support PNG, though it is still far from ubiquitous. We will discuss it after thoroughly examining the GIF and JPEG formats—how they work, which types of images they deliver best, and how you can evolve strong stylistic concepts by understanding their limitations. GIF The Graphics Interchange Format (GIF) is older than the Web. In fact it is older than some web designers. GIF was developed in the 1980s by Com- puServe, and you’ll often hear old-timers speak of “CompuServe GIFs.” You’ll also hear them talk about walking 12 miles to a one-room school- house. The Compuserve folks pronounced the word as if it were the name of the peanut butter (“Jiff”) and because they were the inventors, that is the cor- rect pronunciation. Millions of people pronounce GIF with a hard “G,” how- ever, so you might as well be a sniveling conformist and spend the rest of your career mispronouncing GIF while secretly suffering great guilt over it. GIFs are usually seen with a .GIF file extension, as in payme.GIF or payme.gif. The GIF format renders in 8-bit color or lower, at your discretion. Two-color GIFs are not uncommon. GIF permits you to achieve crude transparency effects by marking one of your 216 (or fewer) colors as “transparent.” How- ever, you must take care to anti-alias the foreground image against the transparent color, lest mismatched halos surround your graphics. Fortu- nately, GIF renders specific colors exactly, so it is an easy matter to match web page backgrounds to image backgrounds. The only caveat there is the previously mentioned heartbreak of 16-bit systems. Above all, GIF enables you to save bandwidth without sacrificing quality. It employs the Unisys-patented Lempel Ziv Welch (LZW) algorithm (www.dogma.net/markn/articles/lzw/lzw.htm) to efficiently compress solid color areas while preserving crisp detail. Though the format necessarily dis- cards colors—for instance, when rendering a 24-bit image as a 16-color GIF—it does not blur or eliminate significant image details. For this reason, the GIF algorithm produces what is known as lossless compression. 222 HOW: Visual Tools: Format This 13 0732 CH09 4/24/01 11:22 AM Page 222 Loves logos, typography, and long walks in the woods This combination of crisp detail and efficient compression makes GIF the format of choice for line art including typography, logos, and illustrations. As mentioned earlier, the GIF format can also be used to create animated images. When combined with JavaScript rollovers, animated GIFs can lend life and dynamism to a website. They can also create nausea and ennui. With animation and rollovers, as with Tabasco, a little goes a long way. Animated GIFs have been supported in all graphical web browsers since Netscape 2.0 (1995), and nonanimated GIFs have been supported in graph- ical web browsers since before time began. For now we will continue to discuss the merits and uses of static (nonanimated) GIFs. In spite of the fact that GIFs are found on millions of sites, the GIF format is not a W3C-recommended web standard. That’s because GIF gets its power from a patented algorithm. Unisys, the patent holder, is entitled to charge royalties on any software that employs the LZW algorithm—in other words, any software that can read or write GIFs. The revelation of Unisys’ right to charge a “GIF tax” spread panic among early web designers when it became widely known only after the entire Web seemed to be built with GIF images. It also led to the development of PNG, a GIF-like format with more advanced features and a nonproprietary compression algorithm. GIF “royalties” do not work in the way that, say, photo rights work. You do not pay a fee each time you create a GIF image. Instead, software compa- nies such as Adobe, Macromedia, and Corel render these tributes to Cae- sar. You pay your share one time only, and it is hidden in the purchase price of Photoshop, Fireworks, or any other software program that exports to the GIF format. GIFs are not the format of choice for photography, paintings, and other subtly modulated images because they lack sufficient colors to reproduce these types of images and because the nuances in those images do not lend themselves to LZW compression. Photographic images tend to render bet- ter in the JPEG format (or PNG), and we’ll get to those formats soon enough. 223 Taking Your Talent to the Web 13 0732 CH09 4/24/01 11:22 AM Page 223 GIFs in Photoshop In Photoshop, you can choose whether to save your image as a standard or interlaced GIF. The standard format is like a reader, taking in one letter after another, one word after another, one sentence after another. Standard GIFs store and display the bytes comprising an image’s pixels in their order of appearance: The first pixel in is the first pixel out. Thus, standard GIFs scroll onto the viewer’s screen pixel by pixel and line by line. The interlaced format is like a nervous reader who keeps skipping ahead— from paragraph one to paragraph five, then back to paragraph one. Inter- laced GIFs load in a parallel rather than linear sequence, allowing the total image to be rendered more quickly and then with greater detail as addi- tional pixels are downloaded. This allows viewers to get a sense of the image before it has finished downloading. Under the right conditions, interlaced GIFs might thus appear to load faster—and so may your site. The appearance is deceptive given that inter- laced GIFs are often a few bytes larger than standard GIFs and therefore take a fractionally longer time to fully download. Moreover, the slight benefits of interlaced GIFs often evaporate when other conditions are factored in. For one thing, the effectiveness of progressive GIFs depends on the viewer’s access speed. With a super-fast connection, images load so quickly that any progressive rendering benefits are lost. The format was something of a godsend not so long ago, when most web users were limited to 14.4 modems. Today, few are stuck with such abysmal speeds. The effectiveness of progressive GIFs also depends on the browser. Some browsers do not show anything at all until all images are fully loaded; in those browsers, the progressive aspects of the image are entirely wasted. If anything, in such browsers, progressive GIFs delay the page by adding a few bytes to the overall download time. Some browsers, such as Internet Explorer, give users a choice. Users may view each image as it downloads (best with slow connections), or they may choose to wait for the entire page to download and assemble itself in mem- ory before appearing full-blown on the screen (best with fast connections). Users choose a viewing method in the Explorer Preferences dialog box. You have no way of knowing or controlling these user preferences. 224 HOW: Visual Tools: Format This 13 0732 CH09 4/24/01 11:22 AM Page 224 Beginning web designers often ask if they can control the loading order of images on a web page. Given what has just been explained, the answer is obviously “no,” because web users can choose (or their browsers may force them) to wait for the entire page to load. Beyond that, HTML has no means of controlling the loading order of images. And even if it did support such nuances, the unpredictability of HTTP calls (explained in Chapter 2) means that one image might halt in mid-download, not even appearing until another, called much later, has already popped into place. The more images per page, the greater the randomness of load order. View a busy thumbnail image gallery sometime to see this in action, assuming your browser allows you to watch images download one by one. Avoid progressive GIFs when creating an image to be used as a background. Backgrounds do not appear until they have fully downloaded, so any “pro- gressive” effects will be lost. Moreover, progressive GIF backgrounds can crash some older browsers. Progressive GIFs also can be hazardous to animations because each suc- ceeding frame of a progressive animated GIF will appear blurry, thus defeating the effort to create smooth motion effects. They’re not great for JavaScript rollovers, either. You can offset the harm- ful, blurred quality of progressive GIFs in rollovers by preloading the images, a technique explained in the Chapter 11, “The Joy of JavaScript.” When preloaded via JavaScript, images download and are stored in the viewer’s cache even though they do not appear on the web page until trig- gered by some action on the viewer’s part (typically, moving the mouse over an image to which rollover effects have been applied). Any sane web designer who creates rollovers starts by preloading the alternate (replace- ment) images. But if the images are going to be preloaded anyway, there’s no sense in having them render progressively because the user will never see them until they have fully downloaded and cached. One last tip while we’re in this area. Given that text loads instantly and images take time (see Chapter 2), designs that use HTML text above the fold will appear to load more quickly than those that bury their text fur- ther down on the screen. A web user waiting for images is a web user with nothing to do (except, perhaps, hit the Back button). A web user reading 225 Taking Your Talent to the Web 13 0732 CH09 4/24/01 11:22 AM Page 225 text has less anxiety about the fact that some images may not have fin- ished downloading. With sufficiently engaging text, the user will feel that the site is responsive. Keep this in mind when designing sites that require a great many images. JPEG, the Other White Meat The Joint Photographic Experts Group (JPEG) format should be familiar to you from stock photo houses, digital cameras, and the Photoshop tutorial itself. Usually seen with a .jpg file extension (as in landscape.jpg), JPEG sup- ports 24-bit color and preserves the subtle hue and brightness variations found in photographs and other continuous-tone images. JPEG is therefore usually the format of choice when creating photographic images for the Web. Like GIF, JPEG is widely supported in visual web browsers. Just as MP3 music files toss away audio harmonics to achieve compact file sizes, JPEG’s compression works by selectively discarding bits of image data. Because a loss of quality is involved, JPEG compression is referred to as lossy compression. “Lossy” is an annoying word that looks wrong, but we appear to be stuck with it. In theory, the material discarded by the JPEG optimization process is data that is nearly invisible to the human eye (just as audio data discarded by the MP3 format is supposed to go practically undetected by your ears, though we’ve never met a music fan who could not hear the difference). The greater the JPEG compression, however, the more visible the “missing data” becomes. At extremely high compression ratios, JPEG images can display funky artifacts (see Figures 9.5 and 9.6). Although JPEG is generally preferred for photographic images, when sharp detail is important, GIF is the better choice. JPEG tends to soften images as it compresses them. Particularly when you are working with typography, the softness of JPEG images can ruin the effect of a web graphic. Naturally, there is a workaround, as explained in the “Combining Sharp and Blurry” section later in this chapter. Unlike GIF, the JPEG format does not retain specific web-safe (or other) col- ors. It promises you a rose garden, but the rose might be umber. In a sil- houetted portrait where the edges of the image must match the background of the web page, you would therefore use GIF, not JPEG. 226 HOW: Visual Tools: Format This 13 0732 CH09 4/24/01 11:22 AM Page 226 227 Taking Your Talent to the Web Figure 9.5 At moderate JPEG compression levels, image details are clear, but file size is high. Figure 9.6 At high JPEG compression levels, file size is low (minimizing bandwidth) but so is the quality. Each JPEG optimization is an exercise in balancing file size versus quality of detail. 13 0732 CH09 4/24/01 11:22 AM Page 227 Photoshop’s Save For Web function provides a small, Matte Color dialog box that purports to save an exact background color of your choice, even in the JPEG format. (Skip ahead to Figure 9.7, if you must. The Matte Color dialog appears at mid-right.) Photoshop does all it can to fulfill this promise, but the JPEG format really is not built to handle specific colors like this. To viewers with 24-bit and higher systems, the background color will appear to match. For 16-bit and lower users, the mismatch may be clearly visible. So stick with GIF when you absolutely, positively, have to deliver a specific web-safe (or other) color. In Photoshop, you can choose whether to save your JPEG as a baseline (standard) JPEG or as a progressive JPEG. Progressive JPEGs display a low- resolution version of the image almost immediately and then gradually come into crisper focus. As with progressive GIFs, under the right circumstances, progressive JPEGs can create the illusion that the site is loading faster. As previously dis- cussed, this varies depending on the viewer’s access speed, browser func- tionality, browser preferences, and the caprices of HTTP. And as in the discussion of GIFs above, when intended as background images, progres- sive JPEGs are a no-no unless you want some of your visitors to crash- crash. Optimizing GIFs and JPEGs When we export images such as GIFs and JPEGs, we choose the format most appropriate to the type of image we’re dealing with and then opti- mize it to create the best appearance possible, while using the least amount of bandwidth and computing resources. In addition to optimizing (reducing file sizes), the exporting process allows us to further exert control over the color of our GIF images. Photoshop 3, 4, and 5 offered early web designers very little in the way of optimization and color controls. As a result, a number of inexpensive, third-party, shareware plug-in products specifically tailored to the needs of web designers sprang up in the mid-1990s, most notably Boxtop 228 HOW: Visual Tools: Format This 13 0732 CH09 4/24/01 11:22 AM Page 228 Software’s PhotoGIF, ImageVice, and ProJPEG (all are available at www.boxtop-software.com). These products were dandy (still are), but they did not come as standard equipment (still don’t). Arguably, they do a bet- ter job than Photoshop at handling some tasks. Fortunately, Photoshop 5.5 and higher, together with ImageReady, offers a number of tools to help web designers create the best-looking image while using the least amount of bandwidth. Photoshop’s Save For Web command (found in File, Save For Web) enables web designers to preview the effects of various compression settings on their images and then execute those settings and save the resulting web-ready images (see Figure 9.7). The Save For Web dialog is powerfully compelling in the breadth and sub- tlety of its tools. You can preview GIF versions using as few as two colors, as many as 256, or anything in between. You can use Adaptive, Selective, Perceptual, or web-safe color, with or without dithering, transparency, or interlacing (the “progressive” setting). You can skew images closer to or further from the web-safe palette as you desire. You also can name and save custom settings for later application to similar images. 229 Taking Your Talent to the Web Figure 9.7 Photoshop’s Save For Web dialog in action. In this “four-up” view, the original image appears at the upper left for easy comparison with various optimization schemes of your choosing. 13 0732 CH09 4/24/01 11:22 AM Page 229 Work on one optimization setting at a time or view three at once—and compare them with the original to check for image degradation and color shifting. Get an instant readout of the effect your decisions will have on file size and downloading speed. Enlarge images to check fine details. Lock selected colors before trying a new set. Shift one color at a time to its clos- est web-safe equivalent. We feel like press agents. We feel giddy. We love this dialog box. You will too. Images in Save For Web mode also may be previewed at various JPEG set- tings, both baseline and progressive, and again the tools are remarkably powerful. In general, the fewer the colors used in a GIF, the better it compresses. This is not because the color palettes themselves eat bandwidth; rather it is because of the way LZW compression works. More on that in a moment in the “Expanding on Compression” section that is coming up next. Dithering images produces more photographic-like effects at the cost of slightly higher file sizes; images without dithering are smaller. We find that typographic GIFs are often cleaner and more legible when saved without dithering. Your mileage may vary. You can create either type of image (and preview the results) in Photoshop’s Save For Web dialog box. After you decide which optimization scheme works best for a given image, the image can be saved in that format. Your chosen settings may be retained indefinitely, and can even be applied (as a droplet) to an entire folder of images. Photoshop lets you name and store as many of these settings as you like. If a series of images you’ve created for Acme Widgets happens to work well in 12 colors with no dithering at 60% web-safe, you can name that set- ting 12color_nodither (or acme_widgets or 60websafe or donaldduck if you prefer). You can then save it forever—or at least until your backup media deteriorates and what’s left of your hair is white and listless. By then we’ll all be living on Mars while our clones do the work, anyway. Alternately, you can use the ImageReady module to satisfy your wanton image compression and formatting needs. But Photoshop’s Save For Web is just as effective, and the true power of ImageReady comes later in the process (and this chapter). 230 HOW: Visual Tools: Format This 13 0732 CH09 4/24/01 11:22 AM Page 230 [...]... 11:22 AM Page 231 Taking Your Talent to the Web Expanding on Compression As explained previously, we compress images to minimize wasted bandwidth and speed the arrival of the web page We’ve shown you how Photoshop optimizes images when preparing them for the Web, so you know all you need to know to handle the basics The following are some extra tips Make your JPEGS smaller You can make your JPEGs even... from the playing field, although not as fast as we’d like.) Depending on the layout, you alternatively could use the old, nonstandard attribute of the HTML table cell tag to position a photographic image in the background of a table cell and then place a type GIF in the foreground The type GIF would have to be the same size as the background image and would require GIF transparency to allow... ones because LZW compression “reads” images left to right and line by line, the same way you’re reading this book If every pixel in a given line is the same color, that line compresses better, and therefore so does the GIF (there’s more to it than that, of course) Ten lines containing 13 0732 CH09 4/24/01 11:22 AM Page 235 Taking Your Talent to the Web all the same color compress better still Basically,... of directors) and typography (a superimposed headline in Meta or Helvetica Neu Condensed Black) The headline requires sharp focus and crisp handling—thus it begs to be a GIF The photograph wants to be a JPEG What’s a mother to do? 231 13 0732 CH09 232 4/24/01 11:22 AM Page 232 HOW: Visual Tools: Format This Usually, what you do is give greater weight to the need for crisp typography and export the entire... JPEG would soften the headline and render the small type as an illegible blur So… Figure 9.10 the image is saved as a GIF because type takes precedence over photographic nuances The image could also have been saved as a PNG But the PNG would have been far larger and not enough browsers fully support the PNG format yet 13 0732 CH09 4/24/01 11:22 AM Page 233 Taking Your Talent to the Web 233 Alternately,... reduce the appearance of JPEG artifacts) by blurring them slightly before compressing them Not all areas of all images react well to blurring, but it’s surprising what you can achieve by blurring, say, a distant sky and sunset while preserving the sharpness of a human subject in the foreground This kind of work requires selecting the parts of the image you want to blur, feathering the edge of the selection... to allow the background to peek through The size of the GIF would be marked up in the table cell attributes to ensure that the cell was the correct size Though this technique works well in almost every graphic browser since the svelte boyhood of Fred Flintstone, it is a lot of silly (and nonstandard) markup—and it’s probably not worth the bandwidth Or you could do what Magdalena Donnea did on the front... Source to see exactly what Magdalena did.) As we said, most of the time, you’ll use the GIF format to ensure that your text is legible You also might consider rethinking the entire design idea in favor of one that is more in keeping with the limitations of the Web (see Figure 9.11) Figure 9.11 The ever-popular “striped” effect that dominated the web in the late 1990s had its roots in a technique to minimize... masking out the parts of the image where sharper focus is important As we said in the beginning, we assume you already know how to do these things in Photoshop If you prefer, you can apply subtle (or not-so-subtle) blurring effects to your entire image in the Save For Web dialog box, but we generally find this method too coarse Blurring, say, an entire portrait makes the subject look drunk—or the viewer... bandwidth-oriented tool had become a stylistic design fetish by the late 1990s, as newcomers to the field fell in love with the CRLI “look” without understanding its utilitarian purpose as a tool of bandwidth compression To these designers, stripes were “webby,” and “webby” was cool As the Web exploded into public consciousness, consumers and ad agencies seemed to agree with this link between “Web” and “cool.” The . Condensed Black). The headline requires sharp focus and crisp handling—thus it begs to be a GIF. The photograph wants to be a JPEG. What’s a mother to do? 231 Taking Your Talent to the Web 13 0732. lend themselves to LZW compression. Photographic images tend to render bet- ter in the JPEG format (or PNG), and we’ll get to those formats soon enough. 223 Taking Your Talent to the Web 13 0732 CH09 4/24/01. Photoshop In Photoshop, you can choose whether to save your image as a standard or interlaced GIF. The standard format is like a reader, taking in one letter after another, one word after another,