EarthWeb sites:

Chapter 9

Adding Graphics to Your Web Pages

CONTENTS

• The Special Nature of Graphics on the Web
  • The Size of Graphics Files
  • Example: Watching Graphical Sites Download
  • Picking Your Web Graphics File Type
• Creating and Manipulating Graphics
  • Creating Graphics for the Web
  • Example: Creating Graphics in Paint Shop Pro
  • Manipulating Web Graphics
  • Example: Creating Thumbnails with LView Pro
• Creating Transparent GIFs
  • Creating Transparent GIFs in Transparency for the Mac
  • Example: Creating Transparent GIFs in LView Pro
• Embedding Graphics in Web Pages
  • Adding Graphics to Other HTML Tags
  • The ALT Attribute
  • The ALIGN Attribute
  • Example: Adding Graphics to Your Web Site
• Summary
• Review Questions
• Review Exercises

Now that you've seen the many ways you can add some character to your text-and use different tags to better communicate your ideas-it's time to jazz up your pages a little bit. Let's add some graphics!

First, though, you should know a couple of important things about placing graphics. Some of these considerations may seem a bit foreign to you, especially if you're a graphic designer or commercial artist. You have to think in a slightly different way about graphics for your HTML pages.

The Special Nature of Graphics on the Web

You may be comfortable using a program such as CorelDRAW! or Adobe Photoshop to create and manipulate graphics. You may already know the difference between a PICT file and a TIF file (and why that difference might be important). You may even know a lot about preparing graphics for professional printing or adding graphics to desktop publishing documents.

But if you've never done any design for the World Wide Web, there's also a good chance that you've never worried about one special graphics issue, even if you are a print design expert. How big is the graphics file that you created? Aside from using the correct graphics format, this issue is the single most important consideration in graphical Web design.

The Size of Graphics Files

Why is the size of graphics files so important? Your Web users have to download your pages to view them, including all the graphics associated with the pages. Couple that fact with the Web speed issues discussed in Chapter 5, and the need for smaller graphics files becomes apparent.

The high-color, high-resolution graphics files that color printers and professional designers work with are generally measured in the number of megabytes of information required to create the graphics file. Each image can take up more space than is available on a floppy disk. Often, special tapes and cartridges are required to transfer these files from the graphics shop to the printer.

A good average size for a Web graphic, on the other hand, is between 10K and 30K-about one to three percent of the size of those high-color, high-resolution graphics. This could be tough.

Example: Watching Graphical Sites Download

Just to get a feel for how all this graphics stuff works, start your Web browser and Internet connection. Make sure that your browser has its preferences or options set so that it downloads graphics automatically.

If you're using Netscape Navigator, use the Netscape home page as your benchmark. If you're not using Netscape Navigator, point your Web browser to http://www.netscape.com/.

Now, as the page downloads, watch the status bar at the bottom of your browser's window. You should be able to watch as your browser downloads the page and the various graphics, and your browser may even tell you how large each graphics file is as you're downloading.

Next, select an individual graphics file on the page, and save it to your hard drive. In Windows 95, right-click a graphic and then choose to save the graphic as a file (in Navigator or Internet Explorer). On a Mac, hold down the mouse button and then choose to save the graphic when the pop-up menu appears (see . 9.1).

Figure 9.1 : Use Netscape Navigator to download Web graphics.

Finally, look at the file, using the Windows Explorer or Mac Finder. Check the file size of the graphic. Notice how small the file is, and remember how long downloading it took. You'll have to be aware of these considerations when you create your Web graphics.

Picking Your Web Graphics File Type

The other thing that you need to concern yourself with is the file type that you're going to use for Web graphics. In general (at least currently), you can choose either of two file types: GIF and JPEG. GIF (CompuServe Graphics Interchange Format) is the more popular among Web browsers, but JPEG (Joint Photographic Experts Group) is gaining popularity and becoming more widely used.

Why have two standards? GIF and JPEG bring different advantages to the table. Let's take a look.

GIF Format Graphics

Any graphical browser supports the display of GIF format files inline, meaning that the browser doesn't require a special viewer for these files. GIFs are compressed graphics, but they tend to lose less image clarity than JPEGs. Images that have smaller color palettes (those that use 256 colors or fewer) often look better in GIF format. GIF is also the file format of choice for creating transparent graphics-graphics that make the Web page appear to be the actual background of the GIF graphic (see the section,"Creating Transparent GIFs," later in this chapter).

Although GIF files are compressed, they tend to be a bit larger than JPEGs, but they decompress more quickly and tend to be drawn more quickly than JPEGs (given the same file size). Another problem with the GIF file format is the fact that it includes certain copyrighted elements that make it less than an open standard for graphics interchange.

The JPEG Format

Gaining on GIF in popularity is the JPEG format, which is widely used by Web designers. JPEG graphics can be viewed in most new graphical browsers without a special helper application. JPEG graphics have the advantage of being better for graphics that have more colors (up to 16.7 million, in most cases) than similar GIF files; in addition, the JPEG files are smaller (look ahead to fig. 9.2). Also, the compression scheme is in the public domain.

Figure 9.2 : The paint Shop Pro interface.

On the down side, JPEGs can be a little more lossy than GIFs, meaning that the higher rate of compression results in slightly lower image quality. JPEGs also take a little longer to decompress than do GIF files. So although the smaller size of JPEG files allows them to be transmitted over the Internet more quickly, the amount of time that it takes to decompress those files sometimes negates this advantage.

Creating and Manipulating Graphics

It's no secret that a lot of Web design has transitioned from manipulating text-based HTML documents to designing and integrating compelling graphics into Web pages. As the Web has become more commercial, its graphical content has become more professional. If you're not up to the task of creating professional graphics, don't worry too much; programs are available that will help you. Also, it's more important that graphics further the usefulness of the text. The graphics in and of themselves are not the point. The point is to make your Web pages more exciting and informative.

It is a fact, however, that Web sites are leaping forward daily into a more professional, more graphical presentation of Web-based information. Commercial artists and designers are continuing to find new niches on the Web. If you're a skilled computer artist, congratulations; this is where you'll put your skills to use. If you're not, that's OK, too. Any Web designer needs to be able to manipulate and edit graphics in a program such as Adobe Photoshop or CorelDRAW!, but you don't necessarily have to create those graphics, if that's not your forte.

Creating Graphics for the Web

As you get started with a program such as Photoshop or CorelDRAW!, keep in mind that the most important consideration in creating Web graphics is the file size. File size isn't generally the first consideration for creating print graphics; almost any print shop or prepress house will accept large storage cartridges or tapes that provide access to your huge full-color graphics. Not so on the Web. Your target is as small as possible-between 15K and 35K for larger (bigger on the screen) files.

You can come up with graphics to use on your Web pages in many ways. Eventually, any graphic that you use needs to be in a standard file format (for example, GIF or JPEG) and relatively small. But how you come up with the final graphic has a lot to do with the information that you're trying to communicate and with your skills as an artist. The following are some of the different ways you might come up with Web graphics:

• Create graphics in a graphics application. Many programs for both professional and amateur artists can output GIF- or JPEG-format files for use on the Web. Among these programs are Adobe Photoshop, CorelDRAW!, Fractal Painter, and Fractal Dabbler.

• Download public-domain graphics. Tons of sites on the Internet allow you to download icons, interface elements, and other graphics for your Web site. At the same time, public-domain clipart collections (such as those available on CD-ROM) can be useful for Web pages.
• Use scanned photographs. Using scanned photographs (especially those that you've taken yourself) is a great way to come up with graphics for your Web pages. Unless you have access to scanning hardware, though, you may need to pay someone to scan the photos.
• Digital cameras. Cameras are available that allow you to take photos that can be downloaded directly from the camera to your computer. While some of this equipment can be very expensive, cameras under $500 do exist, and those photos can easily be converted for use on the Web.
• Use PhotoCDs. Many photo development shops can create digital files of your photographs (from standard 35mm film or negatives) and save those files in PhotoCD format. Most CD-ROM drives allow you to access these photos, which you can then change to GIF or JPEG format and display on your Web pages.

Example: Creating Graphics in Paint Shop Pro

A popular program for creating Web graphics in Windows and Windows 95 is Paint Shop Pro, which has the added advantage of being try-before-you-buy shareware. To download Paint Shop Pro, access the URL http://www.jasc.com/pspdl.html with your Web browser, and find the hypermedia link for downloading the program for your particular version of Windows.

Paint Shop Pro arrives as a PKZip-compressed file archive, so you also need a program on your hard drive to unzip it when the download is complete. (WinZip is available from http://www.winzip.com/.) Then install the program in Windows and start it. You should see a window like the one shown in figure 9.2.

You can use Paint Shop Pro to create a simple graphic, such as a logo or title, for your Web pages. Using the flood-fill tool, for example, allows you to select a color and "pour" it into the window, creating a background color for the rest of your graphic.

Click the fill-tool icon and then choose a color from the color palette. To apply that color to your graphic, click in the graphic window.

Now select the text tool, choose another color from the palette, and click the graphic window. Type your text (your company name, for example) in the dialog box; then click OK. Now you should be able to drag the text around the window. When you have the text arranged correctly, click anywhere in the window to place the text permanently (see fig. 9.3).

Figure 9.3 : Creating a simple graphic.

Before you save this graphic, you should make it as physically small as possible so that it works well on your Web page. To cut the image down a bit, select Paint Shop Pro's rectangular selector tool. Click somewhere near the top left corner of the graphic (at the point you want to make the new top left corner of your cropped image), and drag the mouse pointer to the other side (bottom right corner) of the image. When you release the mouse pointer, a thin box should appear around this slightly smaller portion of your graphic. From the menu, choose Image, Crop, and the graphic is cropped to that size. If everything went well, you have a smaller graphic that is just as useful for your Web site.

Our last step is to save the graphic in a file format that's useful for the Web. Choose File, Save As. In the Save As dialog box that appears, you can select the file type from a drop-down list (see fig. 9.4). Select either GIF or JPEG, type a filename, and click OK.

Figure 9.4 : Saving your graphic in a Web-compatible format.

Now you've created a graphic for use on your Web page. Use the Windows Explorer or File Manager to check the file size. You want the file to be somewhere around 20K-an ideal size for a Web page graphic.

Manipulating Web Graphics

After you decide what graphics to use, the next step is to manipulate and edit those graphics for best use on the Web. The preceding section discussed some of this manipulation (cropping and saving a graphic to make it as small as possible). Following are some other ways to use graphics applications to make your images lean, attractive, and useful:

• Keep graphics small. Creating smaller graphics in the first place, and using the cropping tool to take out backgrounds and extra space, are great ways to keep graphics to a manageable size.
• Use fewer colors. Many graphics applications allow you to decide how much color information should be included in the file. Do you want to use a possible 256 colors or millions of colors? The fewer colors you choose, the smaller your image file will be (see fig. 9.5).

Figure 9.5 : Adobe Photoshop allows you to choose the color bit-depth for a particular graphic.

• Create thumbnail graphics. At times, displaying a large graphic may be necessary, especially if your user chooses to view it. You can give users this option by creating thumbnail graphics in your graphics programs and then using the thumbnails as links to identical (but much larger) graphics files. This method allows you to create pages that contain many images, all of which are scaled down considerably (and, therefore, download more quickly). If a user wants to view one of the graphics at full size, he or she can simply click the thumbnail graphic.

Example: Creating Thumbnails with LView Pro

Another must-have program for most Windows-based Web designers is LView Pro, a shareware graphics-manipulation program. Although the program has some of the same features as Paint Shop Pro, LView is designed less for creating images and more for changing them from one size to another or from one file format to another.

You can download LView by accessing the Web URL http://world.std.com/~mmedia/lviewp.html. Choose the version for your flavor of Windows, down-load it to your computer, extract it from its Zip archive, install it in Windows, and start it.

To resize an image to create a thumbnail, follow these steps:

1. Choose File, Open. The Open dialog box appears.
2. In the Open dialog box, find the image that you want to resize.
3. With the image in a window on the desktop, choose Edit, Resize. The Resize Image window appears (see fig. 9.6).
4. Now you can use the slider controls or enter a new size for your thumbnails. A good rule is somewhere around 75 pixels wide (width is the first field after New Size in the dialog box). Changing the width also changes the height in order to preserve the aspect ratio of your images.
5. When you have finished resizing, click OK.

Figure 9.6 : Resizing graphics in LView Pro for Windows.

When you create thumbnails, you'll probably want to maintain the aspect ratio of the current graphic in resizing, so that LView keeps the height and width of the new graphic at the same ratio as the original graphic, making the thumbnail smaller but similarly proportioned. Don't forget to save the new file with a slightly different name, using the appropriate file extension (GIF or JPG).

Creating Transparent GIFs

One very popular way to edit Web graphics is to create transparent GIFs. This process allows you to make one of the colors of your graphic (generally the background color) transparent, so that the Web page's color scheme or background graphics shows through (see fig. 9.7). Most often, it's used to give the illusion that the graphic is part of your Web page. You can use this method to add impact to your pages and to limit the size of your graphics by doing away with elaborate backgrounds.

Figure 9.7 : Regular vs. transparent GIFs.

To be rendered with a transparent background, a GIF file must be saved in the GIF89a file format. This can be done with Paint Shop Pro, LView Pro, Transparency for the Mac, and many other programs. Saving a file in this format is simply a matter of deciding what color is going to be the transparent color when the GIF is displayed.

Creating Transparent GIFs in Transparency for the Mac

One of the easiest ways to create a transparent GIF on the Mac is to use a simple application called Transparency. You can download the program from the Web page http://www.med.cornell.edu/~giles/projects.html or http://www.med. cornell.edu/~giles/projects.html.

After you download and install Transparency, double-click the program icon to start it. Pull down the File menu and choose Open. In the Open dialog box that appears, open the GIF file that you want to change to a transparent GIF. Your image is then presented in its own window (see fig. 9.8).

Figure 9.8 : Transparency for the Mac, changing a white background to transparent.

Point to the color in the GIF that you want to turn transparent. As you hold down the mouse button, a color palette appears, with the current color selected. If you want that color to turn transparent, release the mouse button. If you want some other color to be transparent (or if you prefer to use no transparency), point to the color that you want to make transparent and release the mouse button. To turn off transparency, simply select the box marked None at the top of the palette.

Now pull down the File menu and choose the Save As GIF89a command. Rename the file (or use the same name, if you want), and save it. The file now should appear in a Web browser as a transparent GIF.

Example: Creating Transparent GIFs in LView Pro

Windows users can create transparent GIFs in LView Pro. To do so, follow these steps:

1. Load the program, and choose File, Open to open a graphics file. The Open dialog box appears.
2. If the file isn't already a GIF image, choose Retouch, Color Depth, and convert the file to a Palette Image.
3. Select 256 colors in the palette creation and quantizing options, and uncheck the Enable Floyd-Steinberg Dithering checkbox.
4. Click OK.
5. Now you can decide which color will appear transparent. Choose Retouch, Background Color and then click the color that should be transparent. You can also use the dropper (click the Dropper button) to select the color that should be transparent (see fig. 9.9).
6. With the correct color selected, choose File, Save As, and save the graphic as a GIF89a. The background color will appear transparent in a Web browser's window.

Figure 9.9 : Click the dropper to choose the transparent color.

Embedding Graphics in Web Pages

When your graphics are created, cropped, resized, and saved in the appropriate formats, you're ready to add them to your Web pages. To add graphics, you use an empty tag called the <IMG> (image) tag, which you insert into the body section of your HTML document as follows:

<IMG SRC="image URL">

or

<IMG SRC="path/filename">

SRC accepts the name of the file that you want to display, and image URL (or path/filename) is the absolute (full URL) or relative path (for a local file or a file in the current directory) to the image. As the first example shows, you can display on your page any graphic file that is generally available on the Internet, even if the file resides on a remote server. For graphics files, however, it is much more likely that the file is located on the local server, so a path and filename are sufficient.

You could enter the following text in a browser:

<HR>
<P>This is a test of the Image tag. Here is the image I want to
display:</P>
<IMG SRC="image1.gif">
<HR>