Can you "paint" in transparent

[musmuris]

Hi,

When you create a new layer over an existing one you can paint over the underlying image. Is there a way to paint transparency over the underlying image?

To explain. I have a drawing of a pixel man, and I want to produce more images of him with different gestures. To do this I want to create a new layer over him and change just the bits I need by overdrawing, but I need to "erase" the bits from the underlying image that I don't want (i.e. paint transparency over it!). Then when it gets flattened it will just have the resultant image.

I've found the layering works better than copying the original as if I make an error then I can just normal erase to see the underlying image again. So there's a difference between erase and painting transparency, if you see what I mean.

Thanks for any advice

[Sarkut]

It is possible to set your color to zero Alpha - Transparency, and Overwrite blending.

Then you could "paint transparency" onto pixels in the active working layer.

It is not something that could then be erased to bring the image back.

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The Undo function could be used to fix errors.

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Making duplicate layers of the original as spares would make it easy to retrace steps.

If you can post an example image and explain a bit more specifically

what you are doing, it might lead to some helpful suggestions.

[musmuris]

To try and illustrate what I mean imagine the following 4-pixel image. In layer 1 I put 3 red pixels. Layer 2 over that has just 1 blue pixel. When merged down the resultant image has 2 red and 1 blue in it as shown below.

What I what to do is (in layer 2) put a transparent pixel that overwrites the pixel below (which isn't transparent in the traditional sense) so that when merged down the result only has 1 red and 1 blue in it.

Does that make more sense? I understand that these may seem slightly odd (and I have a hard time getting my own head around it) - but I figure I can overwrite in a colour so why can't I overwrite transparency

[Sarkut]

Okay. You want to be able to do Merge with Overwrite Blend mode.

Not possible.

The closest to a work-around, would be to choose a background color

that won't be in the final image. Use that color in place of alpha,

then eliminate that color as a final step in the flattened image.

So, if you chose green as that temporary background color,

your set-up would be:

Layer Two . . . Duplicate of Layer One

Layer One . . .Original Image Object

Layer Zero . . Background - All green

You would work on Layer Two. (Top layer)

If you paint a green pixel it would appear as having been erased,

because it now would match the background.

If you then erase that green pixel, it creates a clear spot in Layer Two,

that allows the original image on Layer One to show through.

So, that way, erasing a change you have made would

bring back the original appearance automatically.

After flattening your completed edit, get rid of the green

using the Magic Wand/Delete or Grim Color Reaper plugin.

Edited July 31, 2010 by Sarkut

[musmuris]

Ok - thanks I was using a separate colour and then removing after merging - didn't think to make a layer below with that colour which is obvious now you suggest it!

I know the Gimp has a "colour to alpha" feature that i've found useful (sadly the gimp is just way to complex for me usually!) - do you know if there's a Paint plugin that does that?

cheers again for the help

[Sarkut]

This should work.

Grim Color Reaper

[musmuris]

This should work.

Grim Color Reaper

Thanks Your help is much appreciated.

[Rick Brewster]

"Merge with Overwrite" wouldn't be possible anyway because it would require a 2nd alpha channel (or a system for doing masks)