[gthumb-list] Undesirable metadata time changes

[Greg Mansfield <G Mansfield computer org>]

I have scanned several thousand slides, negatives and prints over the last couple of 
years.  The scanner software (Vuescan) sets the 'Exif.Photo.DateTimeDigitized' when the 
image is scanned.  I set the 'Xmp.xmp.CreateDate' to my best estimation of the date when 
the photo was taken.  The 'Xmp.xmp.CreateDate' uses the ISO 8601 date format.  This format 
allows me to specify reduced accuracy of time, and also a time interval.  In the first 
example, I determined that the photo was taken during the month of July in 1998, so I set 
'Xmp.xmp.CreateDate' to "1998-07".  The second example was taken sometime between 1955 and 
1959, so I set 'Xmp.xmp.CreateDate' to the interval "1955/1959".

Example 1:
EXIF:
0x010d Exif.Image.DocumentName       : 8-1-98 021
0x010f Exif.Image.Make               : Nikon
0x0110 Exif.Image.Model              : LS-4000
0x011d Exif.Image.0x011d             : Transparency
0x8769 Exif.Image.ExifTag            : 114
0x9004 Exif.Photo.DateTimeDigitized  : 2010:08:27 20:20:01
IPTC:
XMP:
Xmp.xmp.CreateDate            : 1998-07
Xmp.iptcExt.DigitalSourceType : Slide


Example 2:
EXIF:
0x010d Exif.Image.DocumentName       : Earl Anderson Dairy Creme
Haeberle Plaza, Niagara Falls
0x010f Exif.Image.Make               : Epson
0x0110 Exif.Image.Model              : PerfectionV600
0x011d Exif.Image.0x011d             : Reflective
0x8769 Exif.Image.ExifTag            : 164
0x9004 Exif.Photo.DateTimeDigitized  : 2009:12:19 20:04:52
IPTC:
Iptc.Application2.Caption     : Earl Anderson Dairy Creme
Haeberle Plaza, Niagara Falls
XMP:
Xmp.xmp.CreateDate            : 1955/1959
Xmp.iptcExt.DigitalSourceType : Print


When I used the gThumb 2.14.1 'Comment' dialog to add a title to these examples,
  1.  'Xmp.xmp.CreateDate' was changed to the 'Exif.Photo.DateTimeDigitized' value and,
  2.  'Exif.Photo.DateTimeOriginal' was also set to 'Exif.Photo.DateTimeDigitized'.
  3.  'Exif.Image.DateTime' was set to the time the title was changed.

I think that these are undesirable changes.  In the first change, my information was 
destroyed.  In the second change, erroneous information is added to the metadata.  I'm not 
sure why the third change was needed.

Example 1 after adding a title:

EXIF:
0x010d Exif.Image.DocumentName       : 8-1-98 021
0x010f Exif.Image.Make               : Nikon
0x0110 Exif.Image.Model              : LS-4000
0x011a Exif.Image.XResolution        : 72
0x011b Exif.Image.YResolution        : 72
0x011d Exif.Image.0x011d             : Transparency
0x0128 Exif.Image.ResolutionUnit     : inch
0x0131 Exif.Image.Software           : gThumb 2.14.1
0x0132 Exif.Image.DateTime           : 2012:01:08 11:55:07
0x0213 Exif.Image.YCbCrPositioning   : Centered
0x8769 Exif.Image.ExifTag            : 220
0x9000 Exif.Photo.ExifVersion        : 2.21
0x9003 Exif.Photo.DateTimeOriginal   : 2010:08:27 20:20:01
0x9004 Exif.Photo.DateTimeDigitized  : 2010:08:27 20:20:01
0x9101 Exif.Photo.ComponentsConfiguration: YCbCr
0xa000 Exif.Photo.FlashpixVersion    : 1.00
0xa001 Exif.Photo.ColorSpace         : sRGB
IPTC:
Iptc.Application2.Urgency     : 0
XMP:
Xmp.dc.title                  : lang="x-default" weaver
Xmp.exif.DateTimeOriginal     : 2010-08-27T20:20:01-04:00
Xmp.xmp.CreateDate            : 2010-08-27T20:20:01-04:00
Xmp.iptcExt.DigitalSourceType : Slide

Example 2 after adding a title:

EXIF:
0x010d Exif.Image.DocumentName       : Earl Anderson Dairy Creme
Haeberle Plaza, Niagara Falls
0x010f Exif.Image.Make               : Epson
0x0110 Exif.Image.Model              : PerfectionV600
0x011a Exif.Image.XResolution        : 72
0x011b Exif.Image.YResolution        : 72
0x011d Exif.Image.0x011d             : Reflective
0x0128 Exif.Image.ResolutionUnit     : inch
0x0131 Exif.Image.Software           : gThumb 2.14.1
0x0132 Exif.Image.DateTime           : 2012:01:08 12:01:21
0x0213 Exif.Image.YCbCrPositioning   : Centered
0x8769 Exif.Image.ExifTag            : 270
0x9000 Exif.Photo.ExifVersion        : 2.21
0x9003 Exif.Photo.DateTimeOriginal   : 2009:12:19 20:04:52
0x9004 Exif.Photo.DateTimeDigitized  : 2009:12:19 20:04:52
0x9101 Exif.Photo.ComponentsConfiguration: YCbCr
0x9286 Exif.Photo.UserComment        : Earl Anderson Dairy Creme
Haeberle Plaza, Niagara Falls
0xa000 Exif.Photo.FlashpixVersion    : 1.00
0xa001 Exif.Photo.ColorSpace         : sRGB
IPTC:
Iptc.Application2.Caption     : Earl Anderson Dairy Creme
Haeberle Plaza, Niagara Falls
Iptc.Application2.Urgency     : 0
XMP:
Xmp.dc.description            : lang="x-default" Earl Anderson Dairy Creme
Haeberle Plaza, Niagara Falls
Xmp.dc.title                  : lang="x-default" Earl Anderson Dairy Creme
Xmp.exif.DateTimeOriginal     : 2009-12-19T20:04:52-05:00
Xmp.iptcExt.DigitalSourceType : Print
Xmp.xmp.CreateDate            : 2009-12-19T20:04:52-05:00

I'm not certain of the intent for gThumb to change these time fields, so I cannot give 
advice on changes to be made.  For my purposes, I made the following patch to prevent any 
date changes:

diff --git a/extensions/exiv2_tools/gth-metadata-provider-exiv2.c b/extensions/e
index 545506e..cf9bc83 100644
--- a/extensions/exiv2_tools/gth-metadata-provider-exiv2.c
+++ b/extensions/exiv2_tools/gth-metadata-provider-exiv2.c
@@ -207,6 +207,7 @@ gth_metadata_provider_exiv2_write (GthMetadataProvider   *se
                        g_file_info_remove_attribute (file_data->info, _KEYWORDS
        }

+#ifdef DATE_TIME_ALTER
        metadata = g_file_info_get_attribute_object (file_data->info, "general::
        if (metadata != NULL) {
                GthMetadata *xmp_metadata = NULL;
@@ -241,6 +242,7 @@ gth_metadata_provider_exiv2_write (GthMetadataProvider   *se
                for (i = 0; _ORIGINAL_DATE_TAG_NAMES[i] != NULL; i++)
                        g_file_info_remove_attribute (file_data->info, _ORIGINAL
        }
+#endif /* DATE_TIME_ALTER */

        if (exiv2_write_metadata_to_buffer (&buffer,
                                            &size,

Thanks,
Greg Mansfield