Incredibly basic GIMP mask question

OK, this is me being very dim again. Apols in advance. What I want to do is use masks to be able to paint in a grey-black cloudy background behind a horse (fine mane, etc).

I’ve added a duplicate layer. The levels-and-desaturate-and-paint bit to create a black horse on white ground I’m fine with.

But when we get to add layer mask, I have a total and utter mental block on whether I need to set opacity to black white or whatever to allow me to leave the black area untouched. And then what do I do? Help!

I know this is really basic but just cannot get my head around it. I’ve watched tutorial after tutorial and they just confuse me more :frowning:

Anyoen brave enough to have a go at talking me through the steps?

Seen this one?

Absolutely. I just seem to have a blind spot, it all seems very complex and if I try to follow the steps it makes no sense. Here’s a screen shot, let’s assume I want to make that into a mask so I can turn the white bits into a painted background while leaving the black bit (which is part of a horses face in the layer underneath) as a horses face.

I’m sure it’s not hard, I just CANNOT get it.

You made a mask by various ways.

You want to apply that mask to an image. The usual way is

Add a layer mask to the image Layer → Mask → Add Layer Mask and choose the white version
Copy the mask image Edit Copy (ctrl - c)
Make the layer mask active by clicking in the mask icon in the layers dialogue
Ctrl-v to paste into the layer mask, gives a floating layer
Anchor the layer Layer → Anchor layer (ctrl → h)

Of course as with most things Gimp there is a utility script at http://chiselapp.com/user/saulgoode/repository/script-fu/
Look for sg-copy-mask-from-above bottom of the filters section.

Download, put it in your Gimp user scripts folder. It shows up in Layer → Copy Layer Mask from Above

Then it does what it says.