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Support for Images and Sound on a Windows Mobile Device

  • Artigo

4/8/2010

Images and sounds can make the user experience more appealing and should be used when they add value for the user. However, when you are developing online content for a Windows Mobile device, remember that connectivity and bandwidth are limited and expensive compared to a desktop computer. In addition, the display area on a Windows Mobile device is much smaller and more easily cluttered than the display area on a desktop computer. Therefore, to support a better user experience, a conservative approach with images is recommended.

Note

Omitting unnecessary images also improves download times. Wide-area wireless data networks usually have a maximum throughput that ranges from 9.6 kilobits per second (Kbps) to 19.2 Kbps.

Images

Many of the images that are on a Web page are transparent spacer images, or decorative images that have little utility. If you want to display an image that is larger than the working section of the display area, the Internet Explorer Mobile browser follows these rules:

  • If Desktop is set, the Internet Explorer Mobile browser displays the image as specified with the <IMG> tag, honoring the height attribute and the width attribute or by using the natural image size when no attributes are specified. Scrollbars will be added to let the user view large images.
  • If Default is set, the appearance of the image depends on its size, the available width within the block element that contains the image, and the current text size setting as follows:
    • If the width of the image is smaller than or is equal to the available width that is within its container (for example, a table cell or the <BODY> element), the image is displayed as specified in the <IMG> tag.
    • If the image is wider than its container, the image is shrunk to fit exactly within the container. The original width of the image determines how much of the image can be scaled down to fit into the container; wider images can decrease to a smaller percentage of their original size than are narrower images. Under no circumstances should an image be wider than the screen width of the Windows Mobile device.
    • The "text size" setting affects the percentage of reduction from the original size of the image. Smaller text setting enables more reduction from the original size of the image.
    • If One Column is set, the Internet Explorer Mobile browser displays only one TD per row. Images that are considered spacer or decorative will be removed according to the following rules.
    • All the images that have image maps will be retained regardless of their respective sizes.
    • All the images that are wrapped in an <A> tag, which serve a functional purpose, are retained.
    • No background images, on <table> or <body> elements, are removed.
    • Any image that is smaller than 15 by 15 pixels will not be included. This size ensures that the smaller icons on some MobileOptimized pages remain on the Web page while spacer images are removed.

Scaling a Web page reduces the quality of many of the images on that Web page. When you design a Web page for the mobile device, consider avoiding images that are wider than the smallest supported viewing area.

Web page designers that set the Mobile Optimize meta-tag will continue to be respected and the Web page will display in the Desktop view.

Supported Image Formats

The Internet Explorer Mobile browser supports the following formats natively:

  • PNG
  • JPEG
  • GIF
  • Animated GIF files
  • WBMP
  • BMP

Additional formats can be added by using third-party software.

Image Maps

The Internet Explorer Mobile browser supports image maps. When you design an image map for the Internet Explorer Mobile browser, remember to keep the images on your image map small and simple. In addition, your image map should communicate to the user some indication of its function.

Background Sounds

Background sounds are supported by Internet Explorer Mobile and can provide interesting effects. The exact codec rates and sample rates that are supported vary. To maximize compatibility and minimize download size, we recommend that you use a raw Pulse Code Modulation (PCM) stream with a single channel (mono), 8 bits of resolution, and a sample rate of 11 kilohertz (KHz).

Note

For Windows Mobile BGSOUND XHTML Element files play only one time. The LOOP attribute is not supported.

See Also

Other Resources

Internet Explorer Mobile Reference
Mobile Web Site Design Overview
Internet Explorer Mobile Overview