2005.06.28 09:09 "[Tiff] Simpler interface than strip-oriented interface", by Katrina Maramba

2005.08.15 14:41 "RE: [Tiff] TIFF Thumbnail", by Ed Grissom

In a previous message, Joris said:

I have observed that not all TIFF images have multiple directories,

The definitive document on thumbnails in TIFF, and related, is the specification supplement that describes the SubIFD tag, which can be found here:


This being said, there are a number of other schemes 'out there'. Here are two of the most common:

- Some software writes thumbnails the 'old-style' pre-SubIFD way. This

  usually results in a two-page TIFF, the second page being a thumbnail
  of the first bigger image. You can detect this situation by checking

There is also the case where there are multiple reduced resolution images -- i.e. multiple "thumbnails" -- although I would probably only call the smallest the thumbnail.

The "number of pages" confuses me -- perhaps you meant "number of IFDs" instead? If not, are you suggesting that the pagenumber tag be used?

And how can the reader determine the directory number(?) in which the thumbnail belongs (so it doesnt have to read the other directories)?

You can't. You have to read the other directories. See the last line of the

following quote from the TIFF 6.0 spec, section 7 p26:

"Multiple subfiles. TIFF readers must be prepared for multiple images (subfiles)

per TIFF file, although they are not required to do anything with images after the

first one. TIFF writers are required to write a long word of 0 after the last IFD (to

signal that this is the last IFD), as described earlier in this specification.

If multiple subfiles are written, the first one must be the full-resolution image.

Subsequent images, such as reduced-resolution images, may be in any order in the

TIFF file. If a reader wants to use such images, it must scan the corresponding

IFD's before deciding how to proceed."

ed grissom