AWARE [SYSTEMS]
AWare Systems, , Home TIFF and LibTiff Mailing List Archive

LibTiff Mailing List

TIFF and LibTiff Mailing List Archive
January 2015

Previous Thread
Next Thread

Previous by Thread
Next by Thread

Previous by Date
Next by Date

Contact

The TIFF Mailing List Homepage
Archive maintained by AWare Systems



New Datamatrix section



Valid HTML 4.01!



Thread

2015.01.07 19:21 "Re: tools to validate a TIFF?", by Scott Ribe
2015.01.07 19:21 "Re: tools to validate a TIFF?", by Scott Ribe
2015.01.11 22:11 "Re: tools to validate a TIFF?", by Scott Ribe

2015.01.11 22:11 "Re: tools to validate a TIFF?", by Scott Ribe

So, OK, the header and single directory are fine, just as expected for this
single-image, single-strip, binary image:

Magic: 0x4949 <little-endian> Version: 0x2a
Directory 0: offset 118772 (0x1cff4) next 0 (0)
ImageWidth (256) SHORT (3) 1<10208>
ImageLength (257) SHORT (3) 1<13216>
BitsPerSample (258) SHORT (3) 1<1>
Compression (259) SHORT (3) 1<4>
Photometric (262) SHORT (3) 1<0>
FillOrder (266) SHORT (3) 1<1>
StripOffsets (273) LONG (4) 1<8>
SamplesPerPixel (277) SHORT (3) 1<1>
RowsPerStrip (278) SHORT (3) 1<13216>
StripByteCounts (279) LONG (4) 1<118764>
XResolution (282) RATIONAL (5) 1<1200>
YResolution (283) RATIONAL (5) 1<1200>
PlanarConfig (284) SHORT (3) 1<1>
ResolutionUnit (296) SHORT (3) 1<2>
Software (305) ASCII (2) 78<fScanX 1.8.8 14-10-30 Co ...>

The question then is about the data in the strip. Is libtiff actually
emitting invalid code words as claimed by certain utilities? Or are some
TIFF readers broken?

The strip data begins with:

26 a0 78 28 20 3e 03 ec

And I'm getting that error message:

ImageIO: Fax4Decode Bad code word at line 1 of strip 0 (x 0)

So is that strip data valid or not? And if not, then I'll start tracing
through libtiff to see how it comes to emit that data.

BTW, in my first post I mentioned having difficulty figuring out what the
difference was between the flows which led to bad images vs good, because it
seemed that I was using libtiff identically. Well, at a higher level there
is a difference in cropping, and the data that results in bad images is
likely to start with a long string of black pixels. I believe that G4
assumes the image starts with white, and if it starts with black requires a
dummy code word indicating 0 white pixels at the start. That sure seems like
where this could be going wrong--whether it's the writer or reader that is
incorrect.

-- 
Scott Ribe
scott_ribe@elevated-dev.com
http://www.elevated-dev.com/
(303) 722-0567 voice