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Victor Kuznetsov
9ca2811938
On a dark/textured background (e.g. grass) the captured alpha map over-estimates the real Gemini sparkle's effective opacity (~0.51 captured vs ~0.31 effective), so the fixed-alpha reverse blend over-subtracts (watermarked - alpha*logo goes negative) and drives the footprint to black -- the white sparkle turns into a black diamond (issue #30, reported by @CoolZimo1). remove_watermark now detects this via _reverse_alpha_oversubtracts (fraction of footprint pixels with a negative numerator > 5%) and inpaints the small sparkle footprint from the surrounding pixels (cv2 NS, cropped to a padded box) instead. Behavior-neutral on the working case: a bright background over-subtracts at ~0%, so reverse-alpha is used and the output is byte-identical to before (verified: demo_banana 0.0 frac vs the issue-#30 grass image 0.61 frac; issue-#30 footprint recovers to background grass with no pit, residual sparkle conf 0.25 < 0.35). Guard is scoped to GeminiEngine: doubao/jimeng already NCC-align their alpha to the actual mark per image, which sidesteps the fixed-alpha mismatch. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>