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69 lines
3.3 KiB
Markdown
69 lines
3.3 KiB
Markdown
# Jimeng (即梦AI) visible watermark capture
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> **Status (completed 2026-05-30):** solid black and gray Jimeng captures were
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> obtained and the detection asset was solved. The asset now supports detection
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> and mask geometry only. Current removal localizes the wordmark and uses the
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> shared fill backend. The text below records the capture and calibration work.
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Goal: capture the Jimeng / Dreamina "★ 即梦AI" visible wordmark over known flat
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backgrounds so we can rebuild and validate the silhouette used by
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`src/remove_ai_watermarks/jimeng_engine.py`.
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## What we learned (verified from the captures, 2026-05-30)
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- Mark: a four-point sparkle icon followed by the "即梦AI" characters, near-white
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semi-transparent overlay, bottom-right corner.
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- Blend model: **alpha compositing with a pure-white logo** `watermarked =
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a*255 + (1-a)*original`, confirmed in sRGB (a linear-light solve made the
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black/gray cross-residual much worse, so the compositing is plain sRGB). An
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L-pair-solve (independent of the L assumption) lands at ~254.6, confirming white.
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- **Alpha is solved from the GRAY capture**, not black: `a = (I - B)/(255 - B)`
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with B a per-capture CUBIC background fit over the non-glyph pixels, averaged
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over channels, at FULL halo extent (down to a~0.02) and UNBLURRED. Gray (bg ~132)
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is the best proxy for real content (the mark sits on bright photo areas, not on
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black). This careful build drops the gray self-residual to ~1.3; an earlier
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max-channel / quadratic-bg / blurred / halo-truncated build (and a black-dominated
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least-squares solve) left a visible outline -- the mask quality, not the method,
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was the limit.
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- Geometry (fraction of image WIDTH, at the captured 2048): asset width ~0.211,
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height ~0.068, right margin ~0.023, bottom margin ~0.023. The mark scales with
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width; a real 1440-wide download matched width_frac ~0.21.
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- **Per-image render variation:** the alpha maps solved independently from the
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black and the gray capture correlate 0.998 but not 1.0 (mean |Δa| ~0.02). Jimeng
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re-rasterizes the mark per generation and jitters its position a few pixels.
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This was one reason the old reverse-alpha path needed alignment and residual
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inpainting. The current path instead detects the silhouette, localizes the
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glyph footprint, and fills that footprint.
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## How to capture (image-edit path, most reliable)
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For each solid-color seed:
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1. Open Jimeng image generation, use the image-edit / reference mode, upload the seed.
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2. Prompt (Chinese preferred):
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`请完全按照原图重新生成这张图片，保持完全一致，不要添加或修改任何内容`
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3. Download the ORIGINAL output file (not a screenshot). Do not crop / edit / re-save.
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The black capture is the key one (white logo on black -> `captured ~= a*255`); the
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gray capture refines the alpha at mid-tones; the white capture confirms the logo is
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pure white (the mark is nearly invisible on white, as expected).
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## Hygiene
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- Original download, never a screenshot. PNG preferred; if Jimeng only gives JPEG, note it.
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- No crop / edit / re-save. Default settings, watermark left ON.
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## Committed inputs
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```
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jimeng_cap_A.png # black seed run through Jimeng
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jimeng_cap_C.png # gray seed
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```
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The A and C captures feed
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`scripts/visible_alpha_solve.py jimeng`. Rebuild the detection asset with:
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```
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uv run python scripts/visible_alpha_solve.py jimeng # or: all
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```
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