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Recomposing an image from RBGA channels

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Hey Dears,

Well, I`ve got a question here, I`ve separated an image into its, well 4 component channels (R, G, B, A) (and edited those), with each of them being grayscale.

Now, question is, how exactly do I recompose those four grayscale channels into a 32bit image?

I`ve searched around for awhile and found this thread (http://forums.getpaint.net/index.php?/topic/20458-channels-and-decomposingrecomposing/); adding back the alpha layer is trivial with the plugin, however I don`t exactly understand how I should proceed with the RGB channels?

Is there a fancy plugin for those as well?

Sorry for my noob questions xd

<3, Sela

"There is no shortcut to work done true and well. The Creators learned this to their sorrow, the first time they made the world."
Githri the Prisoner

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Create a file with 3 layers called "Red", "Green", and "Blue".

Load each grayscale image into the appropriate layer.

Uncheck the Blue and Green layers (by using the checkmark in the layer window).

Select the Red layer.

Use Adjustments > Curves to isolate the red layer:


1) select "rgb"

2) unselect "red"

3) grab the middle of the line and move it to the bottom right corner

This should prepare your red layer.

Turn off the red layer.

Turn on the blue layer.

Select it and repeat the 3 steps above only this time "red" and "green" should be selected.

Do the same thing for the green layer.

Using each layer's property window, change the blend mode to multiply. (I think... or is it additive. Not sure.)

Create a new layer at the bottom filled with white.

Flatten the image.

Apply your alpha channel.

That should do it.

WARNING: This was off the top of my head, so excuse me if it doesn't work.


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As for suggesting plugins, i can recommend you Curves+ from Pyrochild Plugin Pack.

It will simplify your work in extracting a channel from grayscale image. It works like exactly the Curves Adjustment of Paint.net and has almost identical apperance like it. To convert black-n-white image into black-n-red (i.e. grayscale to red-channel only)

Select "Advanced" in "Transfer Map". And set input as "Luminousity" and output as "Red". Similarly do for green layer and blue layer.


This plugin in "advanced transfer map" has support for hypothetical channels like luminousity, yellow, magenta, saturation, hue , alpha etc. You convert grayscale to alpha, change alpha without changeing color of pixel. It has more tools to draw curves than paint.net's inbuilt curves and also an embedded histogram within it. It's a 'must have plugin' If you use channel operations a lot. :)


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