2005.12.22 22:02 "Re: [Tiff] filtering TIFF tags", by Frank Warmerdam

On 12/22/05, Chris Losinger <losinger@earthlink.net> wrote:

either would be fine, for my immediate needs. and, i'll probably end up hacking something in, if there's no built in support.

         but your 'lazy' mechanism would be ideal.

Chris,

I am concerned about this too. My application can end up re-reading directories quite a bit (as different levels of overviews are accessed for instance) and it seems like the directory reading cost could be quite high.

In addition to "big metadata", I also see this happening with big tile/strip size/offset arrays. In a BigTIFF world, for instance, it would be easy to have files with a million tiles.

It should be pretty easy to make the code that reads custom (ie. generic) tags do so in a lazy fashion. But it could be pretty hard for the tags that are loaded directly into the tiff directory structure as other code then just assumes they can be accessed at will.

Perhaps we could look at doing something for the custom/generic tags first which would solve your problem with big metadata values.

Best regards,
--

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