tailieunhanh - Webmaster's Guide to the Wireless Internet part 40

Webmaster's Guide to the Wireless Internet part 40. The Webmaster’s Guide to the Wireless Internet provides the Wireless Webmaster with all of the tools necessary to build the next generation Internet. Packed with the essential information they need to design, develop, and secure robust, e-commerce enabled wireless Web sites. This book is written for advanced Webmasters who are experienced with conventional Web site design and are now faced with the challenge of creating sites that fit on the display of a Web enabled phone or PDA | 362 Chapter 8 Wireless Enabling Your Big Bandwidth Site Figure Continued my ua dev split _ if uagent eq ua type dev close DB return type The script in Figure provides the basic building blocks to detect both the language that the client can accept and the type of device requesting the content against a predefined list of user agents and device types . By using the results of these two subroutines it is possible to alter the presentation of retrieved data depending on the properties of the client. You could add additional methods to this library to extract the number of softkeys a device has or to collect device-specific identification strings such as the subscriber_no displayed in the header for the or the deviceid of a Palm VII PDA. Which environmental variables you choose to examine and how you branch your code is implementation-specific and it is possible to build WML that works on all devices but most instances will benefit from some code branching or redirection. Implementing Wireless Graphics In general wireless images will be of lower resolution color depth and file size than their WWW counterparts. We will discuss the common file formats for images sent over the wireless Internet how to maintain accessibility when images may not be available and some of the more common methods for creating images in the appropriate wireless format. File Formats Several different image file formats are supported on mobile formats with which any Webmaster will be familiar are GIF and JPEG. A format with which traditional Webmasters may not be familiar is that of the Wireless Bitmap WBMP a one-bit depth two-color bitmap. Which particular device supports Wireless Enabling Your Big Bandwidth Site Chapter 8 363 any particular image format is a much harder thing to discern. Some devices support only WBMP images and others support GIF and JPEG and not WBMP. WML that is transcoded to HDML via a gateway may have all of the images .