2016.09.19 16:29 "[Tiff] Accuracy of TIFF Field metadata (COLORMAP)", by
Thread
2016.11.14 20:13 "Re: [Tiff] Right way to make a multi-resolution pyramid", by Kemp Watson
Thanks for all the various opinions. I take it this means there is NO prescribed “right way” to make image pyramids within the TIFF specification; especially since a subresolution subimage of a subresolution subimage is unimplemented in libtiff (which, though not the TIFF spec, appears to be the defacto go-to implementation), and that’s the very definition of an image pyramid :(
W. Kemp Watson
kemp@objectivepathology.com
On 2016-11-14, 2:02 PM, "Even Rouault" <even.rouault@spatialys.com> wrote:
On lundi 14 novembre 2016 13:16:25 CET Kemp Watson wrote:
Hi all:
What is the ³correct² or canonical way to make a (tiled)
>>multi-resolution
pyramid in TIFF?
Most implementations I¹ve seen simply chain top-level IFDs together,
starting with the base or full-res layer, and going smaller from there
>>to
the apex. this seems wrong to me.
This is indeed the accepted practice in the geospatial field for example. I've never seen use of SubIFD mechanism.
Normal chaining + use of NewSubfileType = FILETYPE_REDUCEDIMAGE is sufficient if you have only one full-res layer.
The description of the SubIFD tag indicates it should be used for reduced-resolution images. To make matters more complex, the
>>NewSubfileType
tag, which appears to be a different ³sub-file² type than a SubIFD,
>>since it
can be used for top-level pages/images, also indicates a value for a reduced-resolution image.
And, if a SubIFD is used, should it point to a chain of IFDs at the
>>second
level, or to an image with a SubIFD pointing to an image, ongoing recursively (which appears to me most correct, but most complex)?
From what I can see in libtiff code ( https://github.com/vadz/libtiff/blob/master/libtiff/tif_dir.c#L430), attaching a SubIFD to a SubIFD insn't supoprted on the write side.
W. Kemp Watson
kemp@objectivepathology.comObjective Pathology Services Limited
www.objectivepathology.com
tel. +1 (416) 970-7284