ExifTool Forum

ExifTool => The "exiftool" Application => Topic started by: Leonard WHYTE on February 20, 2018, 06:45:40 PM

Title: Date/Time Shift features changes other data
Post by: Leonard WHYTE on February 20, 2018, 06:45:40 PM
I have a JPG image file.

When I issue 'exiftool "-DateTimeOriginal+=5:10:2 10:48:0" "."' exiftool changes the DTO meta-data tag and nothing else.  File size and other content remains the same.  This is good.
When I issue 'exiftool "-CreateDate+=5:10:2 10:48:0" "."' however, the DTD meta-data tag is updated, but so also is other stuff and the file size changes.  This is NOT what I want.  I just want DTD to be updated.

Is this a bug?  If not, is there a way I can use "exiftool" to modify the DTD tag but make no other changes to the file content?
Title: Re: Date/Time Shift features changes other data
Post by: StarGeek on February 20, 2018, 07:20:28 PM
DTD tag?  Are you mistyping DTO (DateTimeOriginal)?  Or do you mean something else?
Title: Re: Date/Time Shift features changes other data
Post by: Phil Harvey on February 20, 2018, 09:39:20 PM
This is FAQ 13 (https://exiftool.org/faq.html#Q13).

- Phil
Title: Re: Date/Time Shift features changes other data
Post by: Leonard WHYTE on February 24, 2018, 06:34:00 PM
Phil, yes I understand that the file size changes when the tags are updated.  But that, as such, is not my concern.

What I'm looking for in a date changer, is the ability to patch the DTD/DTO tags 'in-place' without changing ANY other tags in the image.  I don't want the image re-written, just patched.

Your software does this when updating DTO, but when I update DTD, it ALSO fools with some other tags.  I'm wondering why you do things differently for the DTO and DTD date changes?  I'm looking for a way to update both tags in place. 

Len
Title: Re: Date/Time Shift features changes other data
Post by: Phil Harvey on February 24, 2018, 11:06:30 PM
Hi Len,

ExifTool rewrites the entire EXIF if any EXIF tags are changed.  The same goes for XMP and IPTC.

- Phil
Title: Re: Date/Time Shift features changes other data
Post by: StarGeek on February 24, 2018, 11:12:45 PM
Quote from: Leonard WHYTE on February 24, 2018, 06:34:00 PM
What I'm looking for in a date changer, is the ability to patch the DTD/DTO tags 'in-place' without changing ANY other tags in the image.  I don't want the image re-written, just patched.

Technically, it rewrites the entire file every time.  It doesn't rewrite 'in-place' or as a patch.  Is that correct Phil?
Title: Re: Date/Time Shift features changes other data
Post by: Phil Harvey on February 24, 2018, 11:17:49 PM
For JPEG files the EXIF, XMP and IPTC sections are separate.  So, for example, if no EXIF tags are changed then that section is just copied as a block.  But any section that has changed tags is rewritten completely.

- Phil