link areas within images

PROPOSAL

I propose using the top left corner of the image as 0,0 (top,left) and

specifying the rectangular areas within the image as top,left,bottom,right

relative to the top left corner of the image, which fits with many of the

existing image models. top,left,bottom,right will be specified as positive

integers (you can't have a link area off the image). If a link area

overlaps another, then the first link area specified in the HTML for the

document would take precedence. Link areas within images should have

several highlighting types, much like Bold, Italics, and Underline for

text, so that link areas on the image can appear transparent to the user (a

rectangular highlight would distract from the rest of the image), some

highlight such as color or brightness change, or have a state showing the

link has been visited. Supporting arbitrary closed polygons as link areas

would require a little more work, but would be a good idea in the long run.



BENEFITS

Besides opening up a large number hypertext applications not currently

possible with HTML because the granularity of image links isn't precise

enough, supporting image links probably avoids some other complexities

threatening HTML. The discussions revolving around PRE and equations

indicate that HTML doesn't provide enough control to produce the kinds of

documents we're used to doing with TeX, FrameMaker, PostScript, etc.

However, those documents, or individual parts of those documents can be

rendered by other applications and returned as images to WWW browsers as

long as areas within those returned images still work as hypertext links. A

rendering application that returns an image, could also return relative

rectangles as valid HTML that would specify the location of a particular

word, phrase, embedded equation, embedded image, etc. dynamically, which

the browser can then add to the HTML for that document while the document

is being viewed.



Kevin Altis

Intel Corporation

SuperComputer Systems Division

Beaverton, Oregon

