1. Forum
  2. Usenet
  3. LINUX.GENTOO.USER

  • [gentoo-user] faded images with Gwenview : bug submitted

    From Philip Webb@21:1/5 to All on Fri Sep 17 09:40:02 2021
    210914 Philip Webb wrote:
    210913 David Haller wrote:
    Gwenview uses color-management via media-libs/lcms, feh does not.
    See "Rendering intent" and "Color profile" under "Advanced"
    in Gwenview's configure dialog. HTH.
    That cb relevant, but I've explored further & have some results.

    When I crop a JPG image with Fotoxx or Gwenview,
    then view it with Gwenview, the colors remain vivid ;
    this is true whether I rename the new version in Gwenview or not.

    It's only when I crop a PNG image in Gwenview
    & save it in place (ie with the same name), that the colors are faded
    & that's only when viewed with Gwenview, not eg with Feh.

    So I can avoid the problem either by cropping only with Fotoxx
    or by renaming them whenever I do it with Gwenview
    or by converting PNGs to JPGs before cropping them.

    I have reconfirmed this.

    The bad case does look like a Gwenview bug,
    but KDE bugs tend to disappear into the ocean, if reported.

    In fact, as I had forgotten (grimace), I did submit a bug previously :
    KDE Bug 420357 back in April 2020, to which no-one has yet responded.
    I've added a comment & we'll see if there's any response this time.

    Thanks for the comments. I will try redoing the faded versions,
    tho' that will mean getting them from the I/net again.

    I managed to do that & now have images which cb seen via Gwenview.

    Any further suggestions re causes of the bad case are welcome.

    They still are, but it does seem to be a bug.

    --
    ========================,,============================================
    SUPPORT ___________//___, Philip Webb
    ELECTRIC /] [] [] [] [] []| Cities Centre, University of Toronto
    TRANSIT `-O----------O---' purslowatchassdotutorontodotca

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Philip Webb@21:1/5 to All on Sun Sep 19 06:10:01 2021
    210917 Philip Webb wrote:
    It's only when I crop a PNG image in Gwenview
    & save it in place (ie with the same name), that the colors are faded
    & that's only when viewed with Gwenview, not eg with Feh.
    The bad case does look like a Gwenview bug,
    & in fact, as I had forgotten (grimace), I did submit a bug previously :
    KDE Bug 420357 back in April 2020, to which no-one has yet responded.
    I've added a comment & we'll see if there's any response this time.

    Tibor Nagy of KDE Bugzilla has replied very promptly :

    My guess this happens due to botched gamma handling.
    Washed out images are a prime symptom of that kind of bugs.
    Seems like when a PNG gAMA chunk is present,
    Gwenview applies the gamma transform in the opposite direction it should,
    thus the washed out images. Seems to be Qt bug, already fixed in 5.15.x :
    https://github.com/qt/qtbase/commit/de2c3ccd49cb89e0c6912da3b03705a36ef03946

    As you can see from the link above, some coder forgot to invert a value,
    using 'gamma' when it sb '1/gamma'.

    The patch is dated 'June 11', so it make take awhile yet to reach Gentoo.

    Meanwhile, I have 2 workarounds which are in fact improvements for me.
    I have amended the Imagemagick 'import' command I use for screenshots
    to produce them as JPGs, which cb safely cropped already via Gwenview. Alternatively, Firefox will make screenshots via R-click on its window
    & the area to be grabbed cb marked on the screen, so already cropped.

    From the beginning, I thought it was a programming bug,
    as it appeared suddenly after a KDE update in spring 2020.

    --
    ========================,,============================================
    SUPPORT ___________//___, Philip Webb
    ELECTRIC /] [] [] [] [] []| Cities Centre, University of Toronto
    TRANSIT `-O----------O---' purslowatchassdotutorontodotca

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Neil Bothwick@21:1/5 to Philip Webb on Sun Sep 19 11:30:02 2021
    On Sun, 19 Sep 2021 00:01:51 -0400, Philip Webb wrote:

    Tibor Nagy of KDE Bugzilla has replied very promptly :

    My guess this happens due to botched gamma handling.
    Washed out images are a prime symptom of that kind of bugs.
    Seems like when a PNG gAMA chunk is present,
    Gwenview applies the gamma transform in the opposite direction it
    should, thus the washed out images. Seems to be Qt bug, already fixed
    in 5.15.x : https://github.com/qt/qtbase/commit/de2c3ccd49cb89e0c6912da3b03705a36ef03946

    As you can see from the link above, some coder forgot to invert a value, using 'gamma' when it sb '1/gamma'.

    The patch is dated 'June 11', so it make take awhile yet to reach
    Gentoo.

    5.15.2 is already in testing, which explains why I was unable to
    reproduce this in the way it hit you, but there was still one washed out
    image I saw.


    --
    Neil Bothwick

    667 - The FAX number of the beast

    -----BEGIN PGP SIGNATURE-----

    iQIzBAEBCAAdFiEE8k9T/rX16EJxEKG692eFu0QSMJgFAmFHAnEACgkQ92eFu0QS MJgANxAAm432DRzMIDLzzxfKC+honSKzzqFz7oYWt3GN5JqHe8qQayXo4PEpmocY OmT3cFyuDBm2uH6caTYhi75YXTO3xsJBOEVwWUEoAYkkATQ0cPD4MV8JeVEbtggA 2W27dPgX/7xcVuvho02fpSPedSjpJH0tY9SdAZt5Jhxf12rGdtByrHPPFRNcFoI2 +nEehrPKozupZXSlYQQ/F082rZxNGnAMQmqYUMDMBaO0gDGZCO/xqF/3A83yPMm6 zyeUq149RcC7SB+O5dHvAHaNLdu8oV8qWpdA0t8ySz00gGL9K9wfEQWUMNBRUlsU 91rCZEdoe8R63EoOZKIj7833+is8R1Cf3bdpm+/OyIWC9UTF7DvGjdOyXcuqSx6E ZoiZLTlGuezR+RX2nRUEPSiE7fUY6G/+LRNsJgAhL9sGo7IWOIZ460v41ejiuQIP cz4S/25+0dw93qF/wDk0zjSOPFEy8QqVKaJDK3wFQCc9nkvU4VEWpxGhcmN2R4Op YnTg47muGnOXHHqCdvyp4lUNmWAGCOnH9StWzpdLHwmM9hDhYSNx/yjIKIiCIIuQ gIgWKfW9a8oNrliK+nFMpbrKRTjdXP3WDaw3ASYPSkVxpJi/1k8ctp6RnjFghGsf XXLluXiNO/cXCvDlNwusF1JCLaslOBRvjzYn2Ch/UEjk71IrwcE=
    =KiGU
    -----END PGP SIGNATURE-----

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Philip Webb@21:1/5 to All on Sun Sep 19 11:40:01 2021
    210919 Neil Bothwick wrote:
    On Sun, 19 Sep 2021 00:01:51 -0400, Philip Webb wrote:
    The patch is dated 'June 11', so it may take awhile yet to reach Gentoo.
    5.15.2 is already in testing, which explains why I was unable
    to reproduce this in the way it hit you,
    but there was still one washed out image I saw.

    I'm using Qt 5.15.2-r3 , which is stable, but -r10 is still testing.
    Probably, the correct version wb part of 5.15.3 or 5.16.1 or similar.

    Meanwhile, the advice has to be don't manipulate PNGs using Gwenview :
    convert them to JPG first.

    --
    ========================,,============================================
    SUPPORT ___________//___, Philip Webb
    ELECTRIC /] [] [] [] [] []| Cities Centre, University of Toronto
    TRANSIT `-O----------O---' purslowatchassdotutorontodotca

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Frank Steinmetzger@21:1/5 to All on Sun Sep 19 18:40:01 2021
    Am Sun, Sep 19, 2021 at 05:37:20AM -0400 schrieb Philip Webb:

    Meanwhile, the advice has to be don't manipulate PNGs using Gwenview : convert them to JPG first.

    Rather, manipulate them with something other than gwenview, which is always better than to use JPG due to compression artifacts (even on very high
    quality settings).

    --
    Grüße | Greetings | Qapla’
    Please do not share anything from, with or about me on any social network.

    People who are not convex with foreign words should not renovate with them.

    -----BEGIN PGP SIGNATURE-----

    iQIzBAABCgAdFiEEVbE9o2D2lE5fhoVsizG+tUDUMMoFAmFHZs0ACgkQizG+tUDU MMquYRAAiiLXBaFp24w8kQARYq49Yrnff1zPgTXsnFG6dJqRdabGs4686lPX2ewK xtmKFKa46OsEFvxcOO97ftgFf5p76VRIxA8JFZjZiA71Y86bntZwIsPau6MDO/sd aWcy7J/mISiF/04Z2Rnerf5Zyw8Qhyk83RbZpASj9wFnDk8zS2/br+PKPitV7GL/ tDp9NUD8ELCN7LmKZVTHaCyFqQ8ztYurIyIJdukwGIrzqU9ErZG50GHEn57kAkPC ui6XtIJGxJ7ka/i30uZSYyjcoeeiySsPAE8NX5DdFiyw8QjsherK0TP2iVfO6Mlu vWDIfadkVHZCtyjwRxVhbR6VXzhOw4XQi3b/aK83kcS3OY1J978AWY5WNsb6bLyD KZ4xg23b7rVyR/uXANq6J/MO7kLiMaDdeKg9E9WSdnIGLlN0QX+UCd5OzgVVLVjS 2Bp3FqRAUBK7iW0wliK4DnxlAA6k5xaqRRFr8TyOY4D7SP3nIiLCh7mtdy6zH0PN tN6Xj3KOk8RpwhdzTHcWx4MZm+Xm71+r9D58Udc1LapJl03GZp0FBc0xkL+v6w9t MTIke+Deqn0KZuxf22kn90efaqRyF7/PPG2/AZw5Wq9MJzv6zJ2x9OY4s7NHcRTB Dz38XN5gImge9vVI5JYCSIEZOpMTcCf0kodtxvGcC5o4UBzohIA=
    =evgG
    -----END P