Affinity Photo 1.6 invert mask not working

[Frances Proctor]

I'm trying to stack two photos one on top of the other and use a rectangle to mask a hole in the top photo to reveal the underneath photo.  I am creating a rectangle above my top photo and dragging it down to create a mask on the top photo. but then I need to invert this so that the center is masked out and the top photo is visible around the edges. I have tried ctrl+i to invert and nothing happens I have tried to set the alpha channel and all I wind up doing is making the whole thing transparent 

[toltec]

You need to make two rectangles and subtract one from the other. Layer > Geometry > Subtract.

 

However, if you would like a nice, fast and very easy method. Create the rectangle and drag it to the nesting position of the image. Not the masking position !

 

Nesting

 

Change the layer blend mode of the rectangle layer to erase.

 

Makes a nice hole 

[Frances Proctor]

That's exactly what I'm looking for!  Thank you

 

[R C-R]

3 hours ago, Angelize said:

I have tried ctrl+i to invert and nothing happens

For what it is worth, that is because you can't invert a rectangle -- it is a shape, not a raster image. Note that the Layer > Invert menu item is greyed out when a shape (or a text or other object) is selected, indicating this.

 

In effect, Layer > Invert does the same thing as the Layer > New Adjustment Layer > Invert Adjustment (Affinity Photo) or Layer > New Adjustment > Invert (Affinity Designer) menu item does, which is to create a 'negative' of the layer by inverting its color channels. Masks don't have color channels so an invert adjustment layer can't be applied to them, but it can be applied shapes, text, & raster images, which you might find useful for some other tasks.

 

As an alternative to the methods @toltec mentioned, for a different kind of 'hole' effect you might try experimenting with stacking the masked 'underneath' layer above the 'top' one instead of creating a mask in the 'top' one to let the 'underneath' one show through. (IOW, do what you described in your first post, but reverse the stacking order of the two image layers & apply the rectangle to the other, now top, layer.) Doing it this way may not always get the effect you want but you can use the rectangle as a mask as is, without having to create two rectangles & subtract one from the other or change the layer blend mode.