Keep the piece's smooth core, then grow it back to restore the true edges.
Removes the wood-knot and grain leaks on the MDF-on-floor photo. Pieces that
are textured themselves are left untouched.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Fit the background brightness from the photo border and subtract it, so
side-lit photos threshold cleanly. The clicked pixel (or, without a click,
the border) decides whether the piece is darker or lighter, replacing the
invert checkbox. Adds the MDF-on-wood-floor photo as a regression fixture.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>