Here's a collection of three macros to simplify your workflow: Alpha utilities.afmacros
With the target Pixel object selected, run either "Clear partial alpha" or "Fill partial alpha".
("Fill alpha of selected pixels" is required by "Fill partial alpha", so do not delete it.)
Now that I've tried it a few times, both techniques almost work. The issue is that alpha-channel pixels still persist, while I would like all alpha channel pixels to either be removed or turned fully opaque and I haven't yet found a good way of doing so in Affinity Photo. I've found the 'solution', though, it's at the bottom.
In your example as well, @telemax, most transparent pixels are removed, but not all.
There is no denying that the latter is cleaner, less alpha pixels, but there's still alpha pixels for some reason and I cannot figure out why. Here is zoomed in:
The solution to this, I found, is to just use the fill tool on the pixel layer with the mask layer being nested.
If anyone has any simpler, better or cleaner solution, I'm all ears!
xuvvy got a reaction from telemax in Removing alpha channels from a layer?