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September 2004
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2004.09.17 12:46 "Re: BigTIFF Tag Value Count issue", by Rob Tillaart
> Rob, am I to understand you like option 3 best, or were you merely signalling
> the possibility?
Primary signalling, but I prefer opt. 3 for the following reasons:
- it creates plenty of room for new TAGS.
- it aligns the smallest field to 32 bit
=> aligns with 32bit processors which are most abundant in the world.
=> no need for masking to access fields
=> OK, 64 bit processors still have to mask.
- more important: debugging a hexdump of an BIGTIFF becomes easier as
one search 32 bit aligned (this point was mentioned a few months ago)
The Number of values must be U64 too as my tag might describe an
additional value for every pixel of the image. And as the image can be >
4gig. this array will too. (see below for example)
I agree that that 4 bytes for datatypes is quite high. However this
opens the door to have dedicated datatypes for dedicated tags, and to
have higher level datatypes (e.g. structs). Imagine a bitmap of the
earth, and my new tag describes an overlay of the strength of the
magnetic flux for every pixel. Or an 'mp3' tag to have background
music, etc
regards,
rob