I am trying to do a somewhat obvious thing - emulating the alha chaneel, interpolate between two images. On image is the paint from the pallette, an the other one is the accumulator.
I also played with the way of choosing the brush size and decided to make it slightly counterintuitive. When you move quickly - you are probably trying to cover a large area, so the brush gets larger. And the other way around.
Click on an image
from the palette, then click on the bottom image. A mixture bar will appear
on the left showing you how much of the image is mixed in. For some
reason the VM my browser is using gives me some weird aliasing whe the
images are scaled. So, if the picture liiks to dark and the images too
jagged - try the appletviewer.