2007.07.05 16:54 "Re: [Tiff] Re: BigTIFF", by Joris Van Damme

Gary,

> We've seen that argument before. I've replied before (amongst other

> the same goes for tiling in TIFF, it was not replies) that

compatible with all >

existing software either. So far, nobody my reply, so let's returning to square one in > contradicted stop part of the discussion. > this

The cases aren't the same. An older TIFF reader will recognize such a file as intended to be TIFF, and will get stuck only when it encounters certain tags. It's always been recognized that newer TIFF versions will have new tags. An existing TIFF reader will not recognize any BigTIFF file as TIFF.

As 99% of TIFF applications are image decoders and encoders, the coming of tiles does amount to exactly the same for the end user as does the coming of BigTIFF. The fact that the total failure to read the actual image is slight later in the process when it comes to tiles, does not change the end result.

As to 'having new tags'... We've a private tag scheme. We can have all new tags we want, at any time. However, none of them is allowed to have an impact on the default rendering of an image by a mainstream viewer. That's how tag extension can usefully work, and that's how we can have new tags for denoting Software or Copyright or whatever. It's essentially different when tiling came about. These are not just 'new tags', this is a new scheme that broke the rendering of the image by a mainstream viewer, as does BigTIFF.

At the end of the day, tiling thus had the same impact on the end user as does BigTIFF. Sure, they're not exactly completely identical operations on all levels. To 99% of actual TIFF image interchange users, that's pretty academical and circumstantial, the 1% being the users of tag viewers, tiffinfo and tiffdump, i.e. professional file format specialists that don't really define file format usage.

Best regards,

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