Display effects?

[Juhana Sadeharju <kouhia nic funet fi>]

I would need display effects:
 -gamma
 -unsharp mask
 -white point
 -equalization

By equalization I mean that if I have a photo of white paper
with hand written text, the paper color should go near white
and text near black. GIMP says paper is now (155,121,83) and
text is (95,62,29).

Note that the brightness and contrast knob in the monitor
have already failed even in basic image viewing. Gamma works
better.

I'm aware of offline tools but they are inconvenient to use
and cause a data explosion.

Now eog does not preserve anything between images, e.g., zoom
value, but the values should be preserved until changed.
Because the suggested effects does not change the original
photo, they are comparable to zoom effect.

Juhana