Alpha channel direct manipulation

MB
Posted By
mike.b
Aug 6, 2003
Views
211
Replies
3
Status
Closed
Hi,
I’ve this problem: I want separate layer mask and RGB pixels. When I create mask from the image, using Ctrl-clicked selection (= selection generated from image’s alpha channel), I get nice grayscale mask containing original alpha channel of image.

But – the image still contains its alpha channel, and when it’s combined with the mask, the transparent areas are even more transparent (alpha multiplication).

So what I’d like to do is killing the alpha in RGB part to of layer (setting to maximum = opaque), while retaining all RGB colors, and using only mask to specify transparency.

The problem is I can’t find a way how to write directly to alpha channel of layer (I don’t mean mask now), or just kill it.

Thanks for help!
Michal
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alpha channel direct manipulation

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TD
Thee_DarkOverLord
Aug 6, 2003
{deleated}
MR
Mark Reynolds
Aug 6, 2003
Mike – your post is very difficult to understand becuase you seem to have invented your own terminology… any discussion is going to be limited without some terminology definitions …

• Alpha channel – is a seperate greyscale channel outside the color channels, which can be eventually used for either opacity, color, texture, or most commonly selections.

• Layer mask – this is a greyscale channel which affects the opacity of a layer alone.

• Layer Opacity – this is contained internally within Photoshop as another ‘channel’ – completely transparent pixels have no retrievable RGB value, as they are invisible.

Layer masks and layer opacity work together to produce a composite opacity.

To make a partially transparent layer completely opaque you will have to Image/fill (using behind) with a chosen color! Very clumsy
EP
Eric Purkalitis
Aug 7, 2003
Mike, I’m not sure what your aiming for exactly, but I sometimes find if I need to do some more elaborate manipulation of channels its best to move them out of the image first.

What I do is go the the channel palette select the channel or mask I want to use and right-click, select duplicate channel and then select new under document. This creates a separate grayscale image of the channel.

If you want to combine it with another channel, go back to your original image. Select the channel, duplicate channel, but instead of new in the document drop down select the new image.

You’ll now have a grayscale image with multiple layers. You convert more channels to layers as needed.

The nice thing about this is you can now use different blending methods between the layers. Maybe overlay, screen, softlight, etc.

When you’ve got what you want merge the layers. You can then cut and paste it into a channel or alpha layer of your original file.

Hope that helps

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