Persimmon art

The image to the right caresses my eye so seductively, it's currently the wallpaper on my Motorola Droid. And a neat thing about it is that I created the effect entirely on the Droid itself (from the original photograph shown in the July 4 post, "Green persimmons").
    Below are four more effects. They resulted from irreproducibly playing around, so I can't specify a recipe or formula.