[Bug 301357] New: Support incomplete dates (without time, day, month), like TIFF DateTime supports

https://bugs.kde.org/show_bug.cgi?id=301357

            Bug ID: 301357
          Severity: wishlist
           Version: 2.6.0
          Priority: NOR
          Assignee: [hidden email]
           Summary: Support incomplete dates (without time, day, month),
                    like TIFF DateTime supports
    Classification: Unclassified
                OS: Linux
          Reporter: [hidden email]
          Hardware: Debian testing
            Status: UNCONFIRMED
         Component: Dates
           Product: digikam

Old photos scanned from paper often have no precise date or time known, but
only with precision of a day, a month, or even a year.  Strangely, e.g.
DateTimeOriginal can only be specified with precision no less than that of a
second.

digiKam (1.9.0 from Debian testing and 2.6.0rc4 from unstable) doesn’t seem to
let me specify a date without time or day or month.  I can add a DateTime
property with such precision using ExifTool, and digiKam can read and display
it in a sidebar, but it cannot use it as the image’s date, e.g. with the Adjust
Time & Date feature: it says the source timestamp is missing.

Reproducible: Always

Steps to Reproduce:
1. Try specifying a date without time, day, or month.

1. Specify such a date directly in the file’s metadata, and try to get digiKam
to import it.
Actual Results:  
No luck.

Expected Results:  
Please add support for imprecise dates.

At first I didn’t notice that digiKam cannot use DateTime, but apparently the
files I tried with had contained a complete date, too.

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=301357

Gilles Caulier <[hidden email]> changed:

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--- Comment #1 from Gilles Caulier <[hidden email]> ---
If i understand your request properly, you want to import image with incomplete
date time stamp, typically with time value and only date.

If i remember relevant code, when item is imported, we get datetime stamp from
metadata and we check if it's valid, typicaly date AND time value are here.

Anyway, if you set date as you want and set time to 00:00:00, it's not enough ?

Can you share an image with your datetime stamp set in metadata to test in
local (if you can attach file to this bugzilla entry)

Gilles Caulier

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--- Comment #2 from Aleksej R. Serdyukov <[hidden email]> ---
(In reply to comment #1)
> Anyway, if you set date as you want and set time to 00:00:00, it's not
> enough ?

No, sometimes I don’t know the day of month, or even the month (or even the
season).

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--- Comment #3 from Aleksej R. Serdyukov <[hidden email]> ---
Created attachment 71644
  --> https://bugs.kde.org/attachment.cgi?id=71644&action=edit
testcase: removed metadata, then ran "ExifTool -DateTime=2005 murka.png"

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[Marcel Wiesweg]

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--- Comment #4 from Marcel Wiesweg <[hidden email]> ---
Apparently both Exif and Xmp support incomplete dates. The data structure which
we use, QDateTime, does not. There would be several involved to properly solve
this wish:

1) General support
 - add a QDateTime derived class to libkexiv2 which support incomplete dates
2) Reading
- add two methods which properly parse incomplete XMP and Exif date strings as
described in the relevant specifications
- use these in getImageDateTime
3) Writing
- add methods to format incomplete date strings
- adapt setImageDateTime
4) check database support, probably need to adapt parsing and formatting
5) Support in digikam's UI
6) Support for writing in the edit widgets

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Varun Herale <[hidden email]> changed:

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--- Comment #5 from Varun Herale <[hidden email]> ---
@ Marcel -

So when adding a QDateTime derived class to libkexiv2, it must give some
default values to the unspecified data. What would be the ideal values for that
?

I mean especially for time values, should the default values be in negative ?

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[Marcel Wiesweg]

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--- Comment #6 from Marcel Wiesweg <[hidden email]> ---
I'd expect 1/1 00:00

I'd do it like

DateTime : public QDateTime
{
    DateTime(const QDateTime &time) : QDateTime(time) {}
}

and add one member which defines until which field the data is valid (year,
month, day, ...)

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--- Comment #7 from Varun Herale <[hidden email]> ---
Created attachment 72810
  --> https://bugs.kde.org/attachment.cgi?id=72810&action=edit
Derived class for QDateTime

What about this class structure ? Is this okay ?

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[Marcel Wiesweg]

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--- Comment #8 from Marcel Wiesweg <[hidden email]> ---
I would do the extra field with flags:

enum ValidFieldFlag
{
HasYear = 1 << 0,
HasMonth = 1 << 1,
HasDay = 1 << 2,
HasHour = 1 << 3,
HasMinute = 1 << 4,
HasSecond = 1 << 5,
HasMicrosecond = 1 << 6,

HasYearOnly = HasYear,
HasYearAndMonthOnly = HasYear | HasMonth
HasDate = HasYear | HasMonth | HasDay
HasTime = HasHour | HasMinute | HasSecond
HasDateTime = HasDate | HasTime
// ... (+subseconds ...)
};
Q_DECLARE_FLAGS(ValidFieldFlags, ValidFieldFlag)
// (declare flags operators outside namespace at the bottom)

ValidFieldFlags validFieldFlags;

// some convenience accessors
bool isComplete() { return (validFieldFlags & HasDateTime) == HasDateTime; }
etc.

// conversion to QDateTime
QDateTime toDateTime() const;

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[Gilles Caulier-4]

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Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Dates                       |Metadata

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[Gilles Caulier-4]

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--- Comment #9 from Gilles Caulier <[hidden email]> ---
Varun,

Some progress to write the dedicated class to manage incomplete date in KExiv2
?

Gilles Caulier

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[bugzilla_noreply]

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[hidden email] changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Metadata                    |Metadata-Hub
            Summary|Support incomplete dates    |HUB : Support incomplete
                   |(without time, day, month), |dates (without time, day,
                   |like TIFF DateTime supports |month), like TIFF DateTime
                   |                            |supports

--- Comment #10 from [hidden email] ---
This entry is illegible for GSoC 2016 project  :

https://community.kde.org/GSoC/2016/Ideas#Project:_digiKam_MetadataHub_improvements

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[bugzilla_noreply]

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--- Comment #11 from Aleksej <[hidden email]> ---
> This entry is illegible for GSoC 2016 project :

I think you mean “eligible” https://en.wiktionary.org/wiki/eligible , not
https://en.wiktionary.org/wiki/illegible

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--- Comment #12 from [hidden email] ---
Is there any news about this issue? I am also affected, and before I invest
significant time working through my scanned photos to add dates (or having to
rework them later when this issue is fixed) I want to decide for the right
tool. And I would be sad to work-around it with exiftool instead of staying
with digikam.

I think the fact that specifications of Exif/Xmp allow incomplete dates is a
very strong point that the GUI would better reflect this.

If I set the correct incomplete dates with exiftool, can I then later continue
using digikam to manage these photos? Suppose I import these photos (with
incomplete set by exiftool) into the digikam database, how does it handle these
dates? When I update some tags and write them into the image files, will the
dates be affected or overwritten?

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--- Comment #13 from [hidden email] ---
Answer to the third question:
My workflow is now:
(0. Remove complete date if previously set in digikam)
1. Set correct incomplete date using  exiftool. (See
http://owl.phy.queensu.ca/~phil/exiftool/faq.html#Q5)
  exiftool -xmp:dateTimeOriginal="1980:09" -xmp:CreateDate="1980:09"
"image.jpg"
2. Import image file into digikam. Dates are ignored as invalid and not added
to database.
3. Add tags to image and write them to image file. Only metadata from database
are written to the image file, dates are not affected.

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