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Anonymous
Hi,

I've always been very impressed by PMview's broad abilities, so I was very surprised when I came across TIFF files that it cannot read or open. I have just created some color TIFF files in a document management program called Docuxplorer (from scans), and when I went to open them, PMVIEW said "ambiguous manufacturer dependent old JPEG compression not supported". Since it is a TIFF, with a tif extension, not sure why PMview thinks it's a jpeg. I have no problem reading b&w Tiffs produced by this program, but the color ones seem to make PMview choke. The TIFF files open fine in Microsoft Office Document Imaging program, so they aren't corrupt.
Any thoughts? Thanks.
(Using PMview 2000 on Win2000 machine)
John Gillis
jgillis@architetto.com
Peter
TIFF files may have two types of JPEG compression. The first JPEG compression type is #6, which is also known as "OLD JPEG". The other type is compression #7, which is known as "TIFF-in-JPEG". The latter is intended to replace the former one in the long run. No applications should use #6 any more.

PMView versions up to v2.32 support "TIFF-in-JPEG" (#7) in full, both loading and saving. However, they do not support the old #6 compression, because there is a myriad of different implementations, many of which are ambiguous. This is an unfortunate result due to ambiguities in the TIFF 6.0 standard specification. Even if an implementation can read one vendor's #6 files, it will not read another vendor's #6 files if the other vendor used a different implementation. Generally, TIFF experts recommend implementors to completely forget about #6, since there is no way you can provide full support for it... (They talk about dozens of conflicting implementations). Writing files of type #6 should be avoided at all cost.

Anyway, I have good news for you! I recently decided to do some more work in this area. The next version of PMView *WILL* read some of the most common #6 files, including the notorious "TIFF 6.0 standard violating" #6 files generated by Wang imaging for Windows.

Could you please e-mail one of the images to pnielsen@tuug.fi so that I can verify that the next version will also read your files. Thanks!

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Peter Nielsen (peter@pmview.com) "If you can dream it, you can do it" JFK.

[This message has been edited by Peter (edited July 07, 2002).]
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