Quoting zhang chi <[EMAIL PROTECTED]>:
> in this tut, after feather,C-i,and C-K is used, but what algorithm is used
> when using Ctrl-k ?
> thank you <gimp-developer@lists.XCF.Berkeley.EDU>
If the layer has an alpha channel then the value of the alpha is
scaled by (1 - S) where "S" is the selection mask's value (which spans
the range '0=not selected' to '1=fully selected' -- the selection is
actually a value from 0 to 255).
If there is no alpha channel then the value of each of the components
(RGB) is scaled by (1 - S) and added to the product of the
corresponding component of the active background color and (1 - S).
For Indexed Mode images, the resulting pixel is the active BG color if
S>0.5 and unchanged if S<0.5
Gimp-developer mailing list