[Digikam-devel] [Bug 148649] New: DigiKam needs a better image scaler

[Dik Takken]

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http://bugs.kde.org/show_bug.cgi?id=148649         
           Summary: DigiKam needs a better image scaler
           Product: digikam
           Version: unspecified
          Platform: Gentoo Packages
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: digikam-devel kde org
        ReportedBy: d.h.j.takken phys uu nl


Version:           0.9.2 (using KDE KDE 3.5.7)
Installed from:    Gentoo Packages
OS:                Linux

Large images that are downscaled to fit the window are too soft. This does not only reduce the perception of the actual level of detail in the image, but it also changes the perception of color. I don't know why the perceived color changes, but it does.

I was just comparing color managed display in both CinePaint and DigiKam. Both applications had the image scaled to fit the window. The image in CinePaint looked slightly warmer than the same image in DigiKam. I was just tearing my hair out to find the cause of the problem, and I almost submitted a bugreport about the mismatch. Also, the image in DigiKam looked relatively soft.

After applying unsharp masking on the image in DigiKam, both sharpness and color matched the CinePaint result.

It looks like the choice of scaler used for image display is more important than I would have guessed... Maybe the scaler from CinePaint can be duplicated to DigiKam?