Version:           1.8.0 (using KDE 4.6.0) 
OS:                Linux

When I single-click on a RAW file (NEF format) in digiKam and it opens up in the image editor, I have a problem while changing the luminosity curve. Namely, if I make an adjustment, and then move the curve back to its starting position (either manually or by hitting reset), the change persists: it doesn't get undone/reversed in the preview. If I then tweak the curve again, the new changes get added onto the new changes. (This isn't just the preview, either: the resulting image after I hit "import" also shows the cumulative adjustments.) The only way to get back to the original state that I've found is to close the image editor and start over. As a result, the luminosity curve feature is completely unusable. This is new to 1.8.0; the luminosity curve worked as expected in 1.7.0.

Reproducible: Always

Steps to Reproduce:
Open Digikam 1.8.0. Go to an album and single-click on a NEF image to open it in the image editor. Make a noticeable change to the luminosity curve (in the "post processing" tab). Notice how the preview changes. Now change the curve back, and notice that the preview doesn't get reverted. Make the change again, and notice how it adds to the previous change, rather than being made afresh. (Repeat the last several steps as desired to see the effect building up.)

Actual Results:  
I had an image with hugely exaggerated curve adjustments.

Expected Results:  
It should have only performed the adjustments matching the curve shown in the luminosity curve window, instead of adding all the adjustments I ever did (and had later undone/modified).