[Image-SIG] Simple Question: Adding an alpha layer?

[Derek Simkowiak]

	I have my new "WalImagePlugin.py" which load the WAL file with a 
default palette.

	But one of the flags in the header can set the transparency of the 
image to either 33% or 66%.

	So my newbie question is: give a new Image with mode "P", what is the 
best way to add a uniform alpha transparency of either 171 (which is 255 
* 67% = 170.85) or else 87 (which is 255 * 34% = 86.7)?

	It seems like the thing to do is convert self.palette from "RGB"  mode 
to "RGBA", and then somehow add the alpha data.  I see "putalpha(band)" 
but I don't know what a "band" is.


Thank You,
Derek Simkowiak