2005.08.08 15:18 "Re: [Tiff] Overlay Hyperlinks On TIFF", by Joris Van Damme

Earlier, I wrote:

uint16: number of clickable areas
per clickable area
    uint32: x

Not that it matters much, and it's probably hypothetical and not meant to be useful, but there's an aligment stupidity here that I might as well correct...

How about this:

uint16: number of clickable areas

uint16: region type
per clickable area
     uint32: x
 ....etc

The region type value can be either of 0: the width and height values are meaningfull, the clickable area is a rectangle

1-65534: the width and height values are to be ignored. Instead, this value describes are radius, and x and y describe the center point of a circular region. This type of region should not be included if XResolution and YResolution tags are in the IFD and have different values, since pixels in that case are not rectangular and a radius in pixels does not make sense. 65535: the widht and height values are to be ignored. Instead, after all regular rectangular regions (region type = 0) and circular regions (region type 1 to 65534) have been checked, and no region is found to comply, the x and y of this type of region that is nearest is said to be clicked. Again this type of region should not be included if XResolution is different from YResolution.

It can happend that multiple regions apply (either rectangular or circular, it cannot happen that more regions of type 65535 apply, except if these regions have identical x and y values). This case is undefined, and application code can de whatever it wants with this. Writers should avoid writing clickable area data with overlapping regions because the behavious in such case is not defined.

Just for the fun of it, though... ;-)

Joris Van Damme
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