[Digikam-users] editing with Color Management enabled is very slow?

[Erik Felthauser]

OS and software: Kubuntu 12.10 with kubuntu-backports ppa (digiKam 3.0.0)
processor: Core 2 Duo T6400 2.0 GHz 800 MHz FSB 2 MB L2 (35 W)
memory: 4 GB - DDR2 800 MHz - 2 DIMMs
monitor colorimeter: ColorHug hardware, with ICC monitor profile set to
"High Quality"

I have applied the monitor profile created with ColorHug in two places: in
the KDE system color settings option, and also in digiKam color management
settings.

My photos are mostly 12MP, JPG or PNG.

When I do not have color management enabled, editing photos is quite fast.
When I turn on color management, editing photos is so slow. Just opening
the editing window takes fully 5 to 8 seconds. Even just selecting an area
for cropping, takes 5 second for the system to catch up, and CPU goes up
very high, 50% just for making selection, 100% for other things. Resize the
selection area takes 5 sec or more.
Turn off color management again, and everything is fast again. Opening edit
window is immediate, selection is immediate, etc.

My questions:

1. Since I have set monitor ICC profile in KDE system settings already, can
I turn off digiKam's own color management, and digiKam will still be
showing the correct colors for my monitor / profile?

2. If yes to question #1, what working color space is digiKam using when
its color management option is turned off? sRGB? sRGB-D65?

3. If yes to question #1, then, I think I only need to turn on color
management in digiKam when I want to do soft-proofing for printer, is that
right? (Since I have applied ICC in system settings?)

4. Is it bad to have monitor profile set in both system and in digiKam?
Does this apply corrections twice, causing over-correction? Or maybe this
is why so slow?

5. Why is it so slow to set color management in digiKam? Is my computer
hardware just too old and slow? If I buy a new computer with Intel i7
processor and 16GB DDR3 memory, will it be fast then? Or is the problem
that digiKam is not yet optimized to be fast with color management editing?

Thank you very much,

Erik
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