LibTiff Mailing List
TIFF and LibTiff Mailing List Archive
August 2005
Previous Thread
Next Thread
Previous by Thread
Next by Thread
Previous by Date
Next by Date
Contact
The TIFF Mailing List Homepage
This list is run by Frank Warmerdam
Archive maintained by AWare Systems
Thread
2005.08.08 15:18 "Re: 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
info@awaresystems.be
http://www.awaresystems.be/
Download your free TIFF tag viewer for windows here:
http://www.awaresystems.be/imaging/tiff/astifftagviewer.html