Convert or copy greyscale image into a selection mask?

[Cooner]

My apologies if this has been covered somewhere before, but I can't find it if it has, and I've been watching some of the hue/luminosity masking tutorials and I don't think they're what I'm looking for (or I'm too dumb to figure out how to adapt them for my use.)

I've been trying to rebuild some of my essential Photoshop Actions into Affinity Photo Macros so I can finally be rid of that beast. One of my Actions I built is called "Outline Overlay" … it basically takes a greyscale image (usually line art), copies it and pastes it into Quick Mask Mode, then goes back into regular mode, creates a new layer, and and fills the selection (from the Quick Mask) with black. The result is a transparent overlay layer with black lineart, the subtle grey aliasing around the edges preserved in the transparency of the pixels.*

I'm having some trouble with that big middle step in Affinity, though. Is there some way, either with a Quick Mask-style mode or some other function, to copy and paste or otherwise convert a greyscale image into a selection area?

*(A somewhat similar result could be made by setting the greyscale layer to Multiply, allowing the white and lighter-grey pixels to show what colors are on the layers immediately below them. But when I'm using this Action it's because I actually need a layer that's empty/transparent except for the linework portion of the image.)

If anyone knows or knows a hack to work around this, I'd appreciate it, thanks!

[NotMyFault]

Hi,

https://affinity.help/photo2/English.lproj/pages/Selections/selections_fromlayers.html

To create a pixel selection from layer intensity (luminosity):

Do one of the following:

• On the Select menu, choose Selection from Layer Intensity.
• On the Layers panel, click the chosen layer's thumbnail while pressing the  OPT and  CMD keys

[Cooner]

6 hours ago, NotMyFault said:

Hi,

https://affinity.help/photo2/English.lproj/pages/Selections/selections_fromlayers.html

To create a pixel selection from layer intensity (luminosity):

Do one of the following:

• On the Select menu, choose Selection from Layer Intensity.
• On the Layers panel, click the chosen layer's thumbnail while pressing the  OPT and  CMD keys

Aaah, thank you! Interesting … I thought I tried this before when I was looking through the Select menu, and it didn't work, it gave kind of a faint translucent copy of the line art that wasn't really useable. But this time it seemed to work fine. I must have put myself into some kind of weird mode or setting with all my poking around the first time I did it. Thanks!

[NotMyFault]

Many you have chosen „selection from layer“ which sounds similar but works totally differently (using the alpha values instead of lightness values to create selection).