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August 2005
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2005.08.08 11:32 "Re: Overlay Hyperlinks On TIFF", by Joris Van Damme
Rob,
> interesting concept, embedding the clickable area in the TIFF needs
> 5 (private) tags per area: {x, y, width, height, URL} or at
> least 3 { x, y, URL} using a closest point algorithm.
I don't think so.
For one thing, you seem to imply you could write a tag per clickable area. That
is incorrect, since tags are supposed to be unique. Thus, encoding only a single
clickable area in a tag, you would be restricted to a single clickable area per
image IFD.
Secondly, since the data (x, y, width, height, URL) is really a whole, I would
not waste 5 different tags on it, but rather encode the data as a whole, in a
tag with datatype byte or unspecified.
Thus, I would rather use a single tag, that has data more or less like this (for
example):
uint16: number of clickable areas
per clickable area
uint32: x
uint32: y
uint32: width
uint32: height
uint16: url length
per url character
uint8: url character
uint8: 0
padding to nearest 32bit boundary
Alternatively, you could use a single private tag to point to a list of private
IFDs, in which the data (x, y, etc) could be encoded in private ifd tags (no
codeallocation with adobe required for these), and that pointed to a next
private ifd for the next clickable area, and so one. While beatiful and very
TIFF, it seems rather overkill though for the little amount of data.
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