How to create a layer mask from existing pixel data?

[lphilpot]

Photo 2 (or 2.1 beta) on Windows 11

Let's say I have a pixel layer I've converted to black & white and I want to use that layer data as a mask on an adjustment layer. I thought (?) the process was:

1. Create the selection for the pixel data by an appropriate means (e.g., Ctrl+A on the source pixel layer, then Ctrl+C)
2. On the Channels tab, create a spare channel from that selection
3. Add the adjustment and select it only (click its thumbnail)
4. On the Channels tab, right-click the newly-created spare channel and select “Load To <layer name> alpha”

When I save the selection I end up with an empty (solid) spare channel, however, so of course the mask on the adjustment layer is empty / solid as well.

It would be nice to have an option on an adjustment layer context (right-click) menu to "Add selection as mask", or at least the ability to directly paste into a mask when it's being edited. When I selected my source layer, Alt+clicked to edit the adjustment mask and tried to paste, it just created a new layer.

My use case in this instance was a photo with a lens flare over some bare tree branches against a bright sky, which washed out the dark branch silhouettes. I thought I would use an inverted high-contrast B&W copy of the flare area (white branches on a black sky) as a mask on an adjustment layer to darken the "real" branches only. But due to the above issue I ended up just painstakingly painting a custom mask over the limbs then tweaking brightness / contrast to minimize the washed-out appearance. Hardly ideal...

Thanks.

[NotMyFault]

The fastest option to convert any pixel data into a mask:

• merge visible (optional / when required)
• Rasterize to mask

the fastest ways to copy a mask into an adjustment or filter layer:

• Just nest the mask layer to it, keep it as separate mask layer
• Before adding the adjustment, selection from layer (mask layer), then add adjustment.

so in principle you can save a lot of clicks by using specific ways creating masks, instead of the correct, but lengthy generic process you have described 

 

[lphilpot]

Thanks. Those work, but the "generic" process wasn't working for me. No worries, they're better anyway.

[smadell]

Good morning, @lphilpot. Here’s a really easy variation of your original method.

First, instead of a Select All, make a luminosity selection. (Choose “Select from Layer Intensity” from the Select menu.) Second, with the selection active, create a mask. That’s it. You don’t have to convert the layer to black and white beforehand. And you don’t need the Channels panel as an intermediary, unless you’ve already made the Adjustment and then want to apply the mask.

[lphilpot]

Thanks!