There are a number of reasons why you may want to slice a large image into pieces and use a table to reconstruct it seamlessly on a web page:
Similarly, if you want to add animation to small areas within an image, it is better to break up the image and animate just the portions that move. This will result in smaller files to download.
At times, you may find that an image contains distinct areas of flat color and distinct areas of soft or photographic images. Breaking the image into sections allows you to save some sections as GIF (the flat color areas) and others as JPEG (for graduated tones), to achieve better optimization and image quality overall. For more information on optimizing images, see Chapter 19 and Chapter 20.
Break the image into separated
linked images instead of using an imagemap. This allows alternative
text (using the
alt attribute) to be added for
each linked section of the image (instead of a single
alt message for the whole imagemap). This makes
the page more accessible for people using non-graphical or
In Figure 13-26, I’ve divided an image into sections ...