2005.03.07 22:36 "Re: [Tiff] Problem decoding G4 FAX tiffs", by Frank Warmerdam

Hi all, my apologies if this problem has come up before - I have searched the mailing list archives but not found anything pertinent.

We have received a complaint from one of our users that our software (which utilises libtiff) is not able to properly display his fax images, although the Windows Fax Viewer is able to display them perfectly.

According to the customer these faxes are all created by "NetSatisfaxtion" fax software, although the images appear to have all been created by something called "Pixel Translations Inc, PIXTIFF".

I have placed an example problem file at http://www.gpsoft.com.au/files/tiff/bad_fax.tif

Also a screenshot of how the image appears rendered with libtiff is at http://www.gpsoft.com.au/files/tiff/no_show.png

If anyone can provide any insight into this it would be greatly appreciated!

Jonathan,

Like Bob, I had no problem displaying it with current CVS libtiff. I did notice that your no_show.png looks a bit like an alignment problem and that the image is an odd width (not a multiple of 8). Any chance your higher level code has problems unpacking bit data that isn't an even multiple of 8 so that it fits into bytes nicely?

In addition to upgraded to the latest libtiff from CVS (or at least the latest public release), I would encourage you to try converting the file to RGBA with tiff2rgba to see if that works. Also, you really ought to explain what libtiff interfaces you are using to read the file (the RGBA interface? TIFFReadScanline())?

Best regards,

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I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com
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and watch the world go round - Rush | Geospatial Programmer for Rent