[Digikam-devel] [Bug 138766] New: JPEG Rotations: Give a warning when doing Lossy rotations (and offer to do lossless when applicable)

[Ari]

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           Summary: JPEG Rotations: Give a warning when doing Lossy
                    rotations (and offer to do lossless when applicable)
           Product: digikam
           Version: unspecified
          Platform: Compiled Sources
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: wishlist
          Priority: NOR
         Component: general
        AssignedTo: digikam-devel kde org
        ReportedBy: ari.reads gmail com


Version:            (using KDE KDE 3.5.5)
Installed from:    Compiled From Sources
OS:                Linux

I'm using Digikam 0.9.0 RC2. There are multiple ways to do image rotations: from the Album GUI, from the Editor (two entries in the menu), possibly more. (not counting free rotation, which is always lossy for jpeg)

I heard one of kipilugins does lossless rotations. I have compiled and installed kipiplugins SVN, but as a newbie user, I have no idea when (and if) this kipiplugin is being used when I rotate the image inside digikam.

I'd like Digikam to clearly tell me, when I rotate a jpeg, if the rotation is Lossy or Lossless. And of course I'd prefer it to do lossless whenever possible.

GThumb tells me this (I'm using Edgy official version), when chose rotate and select the angle, the dialog clearly tells me my rotation is lossless. So for now I am using GThumb to do rotations of 45degree multiples, because I am not sure what DigiKam is doing, which is cumbersome.

Thanks!
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[Gilles Caulier-2]

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------- Additional Comments From caulier.gilles kdemail net  2006-12-13 19:55 -------
No, no, no :

From Album GUI, the JPEG rotation is lossless.

From Editor all rotation are lossless. You loss quality if you rencode an image to JPEG.

In fact all image transformations must be done on lossless format (use PNG conversion from Camera Gui to convert JPEG files for example).

Gilles
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[Ari]

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------- Additional Comments From ari.reads gmail com  2006-12-13 22:06 -------
I'm confused :)

So what is the "lossless jpeg rotation" kipiplugin supposed to do?

Thanks!
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[Gilles Caulier-2]

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------- Additional Comments From caulier.gilles kdemail net  2006-12-14 07:55 -------
Ari,

kipi-plugins jpeglossless rotate JPEG image using an lossless algorithm derived from JPEGTrans tool implementation :

http://websvn.kde.org/trunk/extragear/libs/kipi-plugins/jpeglossless/transupp.cpp?rev=575369&view=auto

In digiKam core, camera gui use the same implementation to autorate JPEG file lossless :

http://websvn.kde.org/trunk/extragear/graphics/digikam/libs/jpegutils/transupp.cpp?rev=575363&view=auto

Gilles
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------- Additional Comments From kde colin guthr ie  2006-12-14 11:15 -------
Gilles,

Could you not do something clever in the GUI?

If the user has not made any modifications to the image yet, you could effectively close the image, do the lossless rotation, and reopen the file again?

Keeps the fidelity as high as possible :)
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[Gilles Caulier-4]

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------- Additional Comments From caulier.gilles gmail com  2008-03-18 12:11 -------
Colin,

No... It's too complicated. Image editor is not designed to work as well. And look my comment #1. You want to play with JPEG in editor => saving transformations using JPEG format is lossy. This is the same problem in Gimp or Photoshop.

Using lossless format as TIFF or PNG is the ultimate solution

Also, if you use JPEG to save an image from editor, there is a red text warning
on the saveas dialog about this format.

For me, it's a workflow problem.

Gilles
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[Gilles Caulier-4]

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------- Additional Comments From caulier.gilles gmail com  2008-03-28 20:44 -------
Arnd,

In editor, like we have a warning in save as dialog about quality lost when user use JPEG file format to store image transformation, there is nothing than we can do anymore in this file...

Gilles
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[Arnd Baecker]

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arnd.baecker web de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED



------- Additional Comments From arnd.baecker web de  2008-03-28 21:02 -------
Yes, with the new warning (which was introduced after 0.9)
in the image editor, I would say this is as explicit as possible.
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