Quoting zhang chi :

http://www.gimptalk.com/forum/topic/My-First-Tutorial-Blending-Images-In-Gimp-106-1.html

in this tut, after feather,C-i,and C-K is used, but what algorithm is used when using Ctrl-k ?

thank you

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

On 3/3/07, saulgoode@flashingtwelve.brickfilms.com < saulgoode@flashingtwelve.brickfilms.com> wrote:

Quoting zhang chi :

http://www.gimptalk.com/forum/topic/My-First-Tutorial-Blending-Images-In-Gimp-106-1.html

in this tut, after feather,C-i,and C-K is used, but what algorithm is

used

when using Ctrl-k ?

thank you

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

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.

Quoting David Gowers :

On 3/3/07, saulgoode@flashingtwelve.brickfilms.com < saulgoode@flashingtwelve.brickfilms.com> wrote:

Quoting zhang chi :

http://www.gimptalk.com/forum/topic/My-First-Tutorial-Blending-Images-In-Gimp-106-1.html

in this tut, after feather,C-i,and C-K is used, but what algorithm is

used

when using Ctrl-k ?

thank you

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

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.

Oops, forgot that case.

Also, there is an error in my description:

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).

The very last term in the sentence should be "S" -- not "(1 - S)".