Truly rotating an image?

[William de Smet]

Hi all,
I am trying to rotate a PNG image and having a lot of difficulties with it.
Of course I tried things like:
- set the angle of img x to x
- rotate img x by x
- set the imageData of image x to the imageData of image x

What I want is true rotatation. So on mouseclicks the image rotates say like
5 degrees each time.
Is this possible without loosing the quality of the original img?

Greetings,

William