I eventually worked out what was happening:
The very act of writing the data added two additional fields to the base IFD
- specifically:
StripOffsets (3 Long): 514, 16771762, 33543010
StripByteCounts (3 Long): 16771248, 16771248, 2496960
They were added by the libtiff code internally (not by my code).
Which meant that the base IFD was larger after writing the data than it was
before. Thus, TIFFWriteDirectory over-wrote the EXIF IFD resulting in the
EXIF IFD being overwritten . and the file therefore failed validation.
Therefore, there's no way to avoid the base IFD being at the end of the
file.
From: Tiff <tiff-boun...@lists.osgeo.org> On Behalf Of David C. Partridge
Sent: 13 April 2023 10:33
To: tiff@lists.osgeo.org
Subject: Re: [Tiff] TIffWriteDirectory() causes problems
Grump
I changed the code so this is done before I write the image data:
//
TIFFSetDirectory(m_tiff, 0);
TIFFSetField(m_tiff, TIFFTAG_EXIFIFD, dir_offset_EXIF);
//TIFFCheckpointDirectory(m_tiff);
TIFFWriteDirectory(m_tiff);
TIFFSetDirectory(m_tiff, 0);
(is CheckpointDirectory() supposed to have the same effect as WriteDirectory
followed by SetDirectory ???)
But while it solved the issue with scanline size, the main IFD ended up at
the END of the file again:
C:\Users\amonra\jhove>jhove "C:\Users\amonra\Documents\Astrophotography\DSS
Test Images\Covington\TestImages\Bias\MasterOffset_ISO200.tif"
Jhove (Rel. 1.26.1, 2022-07-14)
Date: 2023-04-13 10:17:09 BST
RepresentationInformation: C:\Users\amonra\Documents\Astrophotography\DSS
Test Images\Covington\TestImages\Bias\MasterOffset_ISO200.tif
ReportingModule: TIFF-hul, Rel. 1.9.3 (2022-04-22)
LastModified: 2023-04-13 06:46:48 BST
Size: 36040428
Format: TIFF
Version: 6.0
Status: Well-Formed and valid
SignatureMatches:
TIFF-hul
InfoMessage: Unknown TIFF IFD tag: 340
ID: TIFF-HUL-12
Offset: 36040184
InfoMessage: Unknown TIFF IFD tag: 341
ID: TIFF-HUL-12
Offset: 36040196
InfoMessage: Unknown TIFF IFD tag: 50002
ID: TIFF-HUL-12
Offset: 36040244
InfoMessage: Unknown TIFF IFD tag: 50006
ID: TIFF-HUL-12
Offset: 36040256
InfoMessage: Unknown TIFF IFD tag: 50007
ID: TIFF-HUL-12
Offset: 36040268
InfoMessage: Unknown TIFF IFD tag: 50008
ID: TIFF-HUL-12
Offset: 36040280
InfoMessage: Unknown TIFF IFD tag: 50009
ID: TIFF-HUL-12
Offset: 36040292
InfoMessage: Unknown TIFF IFD tag: 50010
ID: TIFF-HUL-12
Offset: 36040304
MIMEtype: image/tiff
Profile: TIFF/IT-MP (ISO 12639:1998)
TIFFMetadata:
ByteOrder: little-endian
IFDs:
Number: 2
IFD:
Offset: 36039970
Type: TIFF
Entries:
NisoImageMetadata:
etc .
I don't (now) issue any TIFF calls from Write() apart from
TIFFScanlineSize(m_tiff) and TIFFWriteEncodedStrip().
I tried issuing another TIFFWriteDirectory call just before I called
TIFFClose, just that resulted in a TIFF that I could read in my code without
any issues, but when I tried to validate it using jHove I got:
C:\Users\amonra\jhove>jhove "C:\Users\amonra\Documents\Astrophotography\DSS
Test Images\Covington\TestImages\Bias\MasterOffset_ISO200.tif" | more
Jhove (Rel. 1.26.1, 2022-07-14)
Date: 2023-04-13 10:27:10 BST
RepresentationInformation: C:\Users\amonra\Documents\Astrophotography\DSS
Test Images\Covington\TestImages\Bias\MasterOffset_ISO200.tif
ReportingModule: BYTESTREAM, Rel. 1.4 (2018-10-01)
LastModified: 2023-04-13 10:26:44 BST
Size: 36039970
Format: bytestream
Status: Well-Formed and valid
SignatureMatches:
TIFF-hul
MIMEtype: application/octet-stream
Or if I specified -m TIFF-hul
:\Users\amonra\jhove>jhove -m TIFF-hul
"C:\Users\amonra\Documents\Astrophotography\DSS Test
Images\Covington\TestImages\Bias\MasterOffset_ISO200.tif"
| more
hove (Rel. 1.26.1, 2022-07-14)
Date: 2023-04-13 10:30:14 BST
RepresentationInformation: C:\Users\amonra\Documents\Astrophotography\DSS
Test Images\Covington\TestImages\Bias\MasterOffset_ISO200.tif
ReportingModule: TIFF-hul, Rel. 1.9.3 (2022-04-22)
LastModified: 2023-04-13 10:26:44 BST
Size: 36039970
Format: TIFF
Version: 6.0
Status: Not well-formed
SignatureMatches:
TIFF-hul
InfoMessage: Unknown TIFF IFD tag: 340
ID: TIFF-HUL-12
Offset: 222
InfoMessage: Unknown TIFF IFD tag: 341
ID: TIFF-HUL-12
Offset: 234
InfoMessage: Unknown TIFF IFD tag: 50002
ID: TIFF-HUL-12
Offset: 282
InfoMessage: Unknown TIFF IFD tag: 50006
ID: TIFF-HUL-12
Offset: 294
InfoMessage: Unknown TIFF IFD tag: 50007
ID: TIFF-HUL-12
Offset: 306
InfoMessage: Unknown TIFF IFD tag: 50008
ID: TIFF-HUL-12
Offset: 318
InfoMessage: Unknown TIFF IFD tag: 50009
ID: TIFF-HUL-12
Offset: 330
InfoMessage: Unknown TIFF IFD tag: 50010
ID: TIFF-HUL-12
Offset: 342
ErrorMessage: Unknown data type: Type = 30068, Tag = 25449
ID: TIFF-HUL-3
Offset: 422
ErrorMessage: Unknown data type: Type = 8307, Tag = 25970
ID: TIFF-HUL-3
Offset: 434
ErrorMessage: Tag 19752 out of sequence
ID: TIFF-HUL-2
Offset: 444
ErrorMessage: Unknown data type: Type = 25701, Tag = 19752
ID: TIFF-HUL-3
Offset: 446
ErrorMessage: Unknown data type: Type = 10606, Tag = 24937
ID: TIFF-HUL-3
Offset: 458
ErrorMessage: Tag 0 out of sequence
ID: TIFF-HUL-2
How can I get that root IFD to be at the start of the file please?
Thanks, David
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