AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2006.06.07 11:39 "[Tiff] Editing a tiff image using libtiff", by Sachin Garg
2006.06.07 12:51 "Re: [Tiff] Editing a tiff image using libtiff", by Joris Van Damme
2006.06.12 13:59 "Re: [Tiff] Editing a tiff image using libtiff", by Sachin Garg
2006.06.12 15:09 "Re: [Tiff] Editing a tiff image using libtiff", by Joris Van Damme
2006.06.13 07:29 "RE: [Tiff] Editing a tiff image using libtiff", by Tillaart, Rob van den
2006.06.13 16:02 "Re: [Tiff] Editing a tiff image using libtiff", by Joris Van Damme
2006.06.13 08:32 "Re: [Tiff] Editing a tiff image using libtiff", by Gerben Vos
2006.06.13 08:55 "RE: [Tiff] Editing a tiff image using libtiff", by Tillaart, Rob van den
2006.06.13 16:04 "Re: [Tiff] Editing a tiff image using libtiff", by Joris Van Damme
2006.06.14 09:08 "Re: [Tiff] Editing a tiff image using libtiff", by Gerben Vos

2006.06.13 08:55 "RE: [Tiff] Editing a tiff image using libtiff", by Tillaart, Rob van den

> Cc: Tillaart, Rob van den
> Subject: Re: [Tiff] Editing a tiff image using libtiff

An additional way to handle space is the introduction of an 'alloc-tag'. This tag indicates the size of the 'allocated' block in the file in contrast to the size tag which indicates the count of the bytes used.

There are already the FreeByteOffsets and FreeByteCounts (288 and 289) tags for keeping track of unused space. Nothing is specified about in which IFD they belong, though (the first? the last? wherever you want, and use all of them together?). The spec also says: "not recommended for general interchange", probably partly because of this, and also because it's not very nice to give someone a space-wasting file, I guess :-).

>                                       Gerben Vos.> 

I agree, if a file can be rewritten with zero space-waste it is preferred. The original discussion triggered me to think about how to prevent unnecessary growth by only appending new information at the end of the TIFF file.

In my thought experiment every tile/strip has its own 'alloc-tag' so it should be clear where it belongs to. This 'alloc-tag' is written when the the tile is written first time and its content does not change, unless new space is allocated at the end of the file. Free space is calculated when needed, this in contrast to the FreeBytesOffsets/Counts model in which the list of free space should be kept up to date.

Thanx for your comment,
Regards
Rob

This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law.
If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited.
If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message.
Thank you for your cooperation.