[digikam] [Bug 337691] New: Select 16 Bit Depth as Default for highres jpg: Standard Option or Alternative

[Christian-2]

https://bugs.kde.org/show_bug.cgi?id=337691

            Bug ID: 337691
           Summary: Select 16 Bit Depth as Default for highres jpg:
                    Standard Option or Alternative
           Product: digikam
           Version: 4.1.0
          Platform: unspecified
                OS: All
            Status: UNCONFIRMED
          Severity: wishlist
          Priority: NOR
         Component: Color Management
          Assignee: [hidden email]
          Reporter: [hidden email]

Many users decided to work in jpg workflow with high res cameras.
DigiKam supports 16Bit depth, but jpgs will always be opened in 8Bit
Resolution.

Suggestion 1: Default Depth for JPG should be 16 Bit (Auto-Conversion)
              - an option to open jpgs with 8 Bits is added to the settings

Suggestion 2: Default Depth for JPG should be 8 Bit
              - an option to open jpgs with 16 Bits is added to the settings

Note: Jpgs are already transformed to 8 Bit when saving without warning. Thats
fine for me.

Reason: Most corrections need 16Bit depth for computation, one does not know
what corrections are needed when opening an image. Best choice is alwas work in
16 Bit depth with jpgs (unless very old hardware is used).

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[Christoph Feck]

https://bugs.kde.org/show_bug.cgi?id=337691

Christoph Feck <[hidden email]> changed:

           What    |Removed                     |Added
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                 CC|                            |[hidden email]

--- Comment #1 from Christoph Feck <[hidden email]> ---
Can you provide a link to the specification of 16 bit JPEG?

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[Christian-2]

https://bugs.kde.org/show_bug.cgi?id=337691

--- Comment #2 from Christian <[hidden email]> ---
(In reply to Christoph Feck from comment #1)
> Can you provide a link to the specification of 16 bit JPEG?

Hi Chris,

The latest Jpeg specs are all restricted to 8 bit. The conversion to 16 bit
color depth in digiKam should take place after opening an 8 bit jpg without any
user action to minimize computation errors.
The conversion back to 8 bit is already implemented.

Christian

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[Christoph Feck]

https://bugs.kde.org/show_bug.cgi?id=337691

--- Comment #3 from Christoph Feck <[hidden email]> ---
Ah, I now understood this request. You want the JPEG loader to convert the data
to 16 bit internally before doing any further operations, so that you do not
have to do it manually after each load. Makes sense.

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
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                 CC|                            |[hidden email]

--- Comment #4 from Gilles Caulier <[hidden email]> ---
Converting 8 bits image to 16 bits will introduce noise to fill histogram holes
:

https://projects.kde.org/projects/extragear/graphics/digikam/repository/revisions/master/entry/libs/dimg/dimg.cpp#L2757

Gilles Caulier

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[Christian-2]

https://bugs.kde.org/show_bug.cgi?id=337691

--- Comment #5 from Christian <[hidden email]> ---
(In reply to Gilles Caulier from comment #4)
> Converting 8 bits image to 16 bits will introduce noise to fill histogram
> holes :
>
> https://projects.kde.org/projects/extragear/graphics/digikam/repository/
> revisions/master/entry/libs/dimg/dimg.cpp#L2757
>
> Gilles Caulier

I am not an expert in digital imaging. But as far as I can see the results, the
artificial noise is a minor problem compared to artefacts caused by 8 bit
rounding errors.

The noise is added to the 8 bit version before the transformation takes place?
Or in 16 bit mode? Noise in 8 bit mode would be a drawback for jpgs with less
than 12 MP.

Well distributed entropy in 16 bit mode might be cleaned when the colors are
transferred back to 8 bit mode. I can't tell. My results where fine in print
and on a high resolution / wide gammut monitor using argb profile for 20 MP
jpgs.

But this is no proof in any way.

I will continue using the 16 bit conversion before I apply gradiation and the
like - artefacts/gradients are worse than noise for me.

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

--- Comment #6 from Gilles Caulier <[hidden email]> ---
Look in code, noise is apply to 16 bits image during conversion from 8 to 16.

Gilles Caulier

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[Christian-2]

https://bugs.kde.org/show_bug.cgi?id=337691

--- Comment #7 from Christian <[hidden email]> ---
(In reply to Gilles Caulier from comment #6)
> Look in code, noise is apply to 16 bits image during conversion from 8 to 16.
>
> Gilles Caulier

Thank you. Auto-Conversion to 16 bit would be a great feature for me.
Dont know if is wanted by others.

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Color Management            |Image Editor

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[Gilles Caulier-4]

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Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Select 16 Bit Depth as      |Add a new option to convert
                   |Default for highres jpg:    |JPEG in 16 Bits Color Depth
                   |Standard Option or          |
                   |Alternative                 |

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Add a new option to convert |FILEIO : Add a new option
                   |JPEG in 16 Bits Color Depth |to convert JPEG in 16 Bits
                   |                            |Color Depth

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|FILEIO : Add a new option   |FILEIO : add a new option
                   |to convert JPEG in 16 Bits  |to convert automatically
                   |Color Depth                 |JPEG file in 16 bits color
                   |                            |depth

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|FILEIO : add a new option   |FILEIO : add new option to
                   |to convert automatically    |convert automatically JPEG
                   |JPEG file in 16 bits color  |file in 16 bits color depth
                   |depth                       |

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=337691

--- Comment #8 from Gilles Caulier <[hidden email]> ---
Maik,

Technically, this one is very simple to implement, as all background code is
already here.

A new option must be add to FileIO settings to convert automatically JPEG to 16
bits color depth. This must be available only for Editor and BQM. Other part of
digiKam must still use 8 bits color depth for performance reason.

In JPEGLoader, loading file must apply DImg::convert8to16bits method in case of
option is on.

Gilles

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[bugzilla_noreply]

https://bugs.kde.org/show_bug.cgi?id=337691

[hidden email] changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|ImageEditor                 |ImageEditor-FileIO

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[hidden email] changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|FilesIO-Engine              |FilesIO-JPEG

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