[Gimp-developer] what algorithm is used in Ctrl-K?

[David Gowers]

On 3/3/07, saulgoode at flashingtwelve.brickfilms.com <
saulgoode at flashingtwelve.brickfilms.com> wrote:
>
> Quoting zhang chi <zhangchipr at gmail.com>:
>
> >
> http://www.gimptalk.com/forum/topic/My-First-Tutorial-Blending-Images-In-Gimp-106-1.html
> <gimp-developer at lists.XCF.Berkeley.EDU>
> >
> > 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 at 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


For Indexed Mode Images, the resulting pixel is the active BG color if the
layer has no alpha and S > 0.5, (emptiness) if S > 0.5 and the layer has an
alpha channel, and unchanged if S < 0.5.
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