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16.8 Server Side Image Maps

417

ISMAP Alternative Server Side Image Maps

ISMAP

 is an optional attribute of the 

IMG

 element and can be used in a simi 

lar manner to the 

FORM

 entry. 

ISMAP

 is not

actually a 

FORM

 element at all, but can still be used for simple connections

to servlets or CGI programs. If an image with 

ISMAP

 is inside a hypertext

link, then clicking on the image results in the coordinates of the click being

sent to the specified URL. Coordinates are separated by commas and are

specified in pixels relative to the top left corner of the image. 

For instance, Listing 16.6 embeds an image that uses the 

ISMAP

 attribute

inside a hypertext link to 

http://localhost:8088/ChipTester

, which is

answered by the mini HTTP server developed in Section 16.12. Figure

16 23 shows the initial result, which is identical to what would have been

shown had the 

ISMAP

 attribute been omitted. However, when the mouse

button is pressed 271 pixels to the right and 184 pixels below the top left

corner of the image, the browser requests the URL 

http://local 

host:8088/ChipTester?271,184

 (as is shown in Figure 16 24). 

If a server side image map is used simply to select among a static set of

destination URLs, then a client side 

MAP

 element is a much better option

because the server doesn't have to be contacted just to decide which URL

applies. If the image map is intended to be mixed with other input ele 

ments, then the 

IMAGE

 input type is preferred instead. However, for a

stand alone image map where the URL associated with a region changes

frequently or requires calculation, an image with 

ISMAP

 is a reasonable

choice. 

Listing 16.6 IsMap.html 

The ISMAP Attribute

Select a pin: