Wavelet-decompose doing magic

[Krikor]

I didn't comment on the previous post (so as not to lengthen it even more), but I opened another image with a transparent background and wavelet-decompose replaces the transparency with a black background. That didn't surprise me that much, I actually thought it was normal.

I had also never applied this filter to images with transparent backgrounds before.

But on a layer where the background was cut out, wavelet-decompose having the ability to recreate it... that disturbed me a little. 

If you pay close attention you will see that in the group created by wavelet-decompose only scale1 respects the situation of the layer at the time the filter is applied.
Other scales and the residual scale add the background that had been removed before.

The fact that the filter acts correctly when applying scale 1 makes me think that there may be an error in the filter code for the other layers and the residual. But this is pure supposition.

Okay, the solution is to apply the mask at the end of the process to eliminate the background that was recreated by the filter.
In my case, as I had created the outline with the Path tool, it basically involves doing the initial steps again: Path to selection, invert, delete.

PixLab, thank you.