Everyone sees colors differently, particularly when they are looking at a computer monitor. When you create your FrontPage®-based web, keep in mind the factors that influence how people see color: the settings they have chosen for their computer display, the number of colors you have chosen for your Web site, and the ways in which you employ color. Web pages typically use color in graphic elements, background and foreground colors, and font colors.
When you create an image for display on a Web site, you must decide how many colors to use. Although computers are capable of displaying millions of colors, many computer users have their displays set to 8-bit color, which displays only 256 colors.
If your Web site is aimed at the largest possible audience, it makes sense to use only as many colors as can be seen by all users, which means using no more than 256 colors. Files in the JPEG format can display millions of colors, while files in GIF format can display no more than 256 colors. Read Optimizing Graphics for Web Sites for more information on choosing a file type for your graphic.
Dithering is a method of displaying graphics that uses combinations of colors to approximate the appearance of other colors. Dithering is an issue when a browser displays a graphic that contains colors that are not in the browser's palette of colors.
In general, images look better on the Web if they are not dithered. Dithering can lead to awkward blocks of color. You can avoid dithering by using a limited number of colors.
When you create an image in a graphic editor, you can control whether or not the image is dithered, and what dithering method is used. For example, when you create a custom palette in Microsoft PhotoDraw™ and Microsoft Image Composer, you can choose from error diffusion, random, patterned, or solid dithering.
Each type of Web browser displays colors somewhat differently. This is because each browser has its own palette. A palette is the array of colors that a browser uses to display an image.
The number of colors a palette contains can influence the size of the graphics file and the time it takes to download the file: the greater the number of colors, the larger the file, and the longer the download time.
There are a number of "Web-safe" or "browser-safe"palettes available from various Web sites. These palettes will help graphics be displayed in any browser without dithering. Web-safe palettes are usually limited to 216 colors to reserve the remaining colors for the operating system and browser. A good general rule is to use a Web-safe palette whenever possible.
A popular way to use graphics on Web sites is to use transparency to make one or more elements stand out. Typically, a transparent background color around an irregularly shaped image will make that image stand out.
Choosing a transparent color is an important decision. Many people choose white to be transparent. This decision can lead to problems, for although an image might be surrounded by white, it might also contain white. When you create a graphic that includes transparency, choose a transparent color that is confined to very specific areas that are not part of the image. Magenta is often used as a transparent color for it rarely appears in images.
Another way to use transparency is for a background image, or watermark, over which you place text or other images. A common use of this technique is placing repeating images of a company logo as a partially transparent background.
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