Enblend layers (was Re: [ptx] PTmender Version 0.2 "The enlightment")

[Andrew Mihal]

On Sun, 15 Jan 2006, Daniel M. German wrote:

>  Andrew> Do you want to find an intuitively-editable layer mask such that image A,
>  Andrew> image B, the layer mask, and photoshop normal blending mode equals the 
>  Andrew> same as the Enblend result?
> 
> Yes, that is the idea. 

With photoshop blending modes, each output pixel is a function of the
corresponding layer A pixel, layer B pixel, and mask pixel. In Enblend,
each output pixel is a function of a neighborhood of layer A pixels, layer
B pixels, and mask pixels. These neighborhoods can be quite large as they
grow exponentially in the number of blending levels you use. And you have
to consider various boundary conditions (wraparound +/- 180 or not). I 
think it is impossible to reduce this behavior to a function of only three 
pixels that works for every pixel in the image.

Andrew

-----------------------------
Andrew Mihal
www.eecs.berkeley.edu/~mihal
mihal at eecs.berkeley.edu