The first version swapped a material onto the earcups without changing their
outline, so nothing in the result showed that the alpha channel is being
inpainted too - the silhouette moved by 47 pixels.
The mask now covers both earcups plus a ring of the transparent background
around them (25.1% of the frame, 70.9% of it on the headphones), and the
instruction asks for the earcups to be rebuilt as oversized turbine cups that
flare out past their old outline. The rebuilt region grows 11735 pixels of new
silhouette over what used to be empty background, 100% of it inside the mask,
while the headband, stitching, yokes and hinges stay pixel-identical (0.27/255
mean channel difference outside the mask).
A 25% mask is still clean here; the earlier 16% guidance came from a picture
whose mask had far less context left around it.
Also verified that the alpha is a real channel rather than a trimmed-off fourth
one: re-running with the identical RGB and a fully opaque alpha changes the
masked region by 61.9/255 on average (max 254).
scraed
93b90fad99
