Doubao visible watermark capture

Status (captured 2026-05-29; asset rebuilt 2026-05-31): the black and gray captures are committed here. The generated alpha asset is now a detection silhouette and mask-shaping input only. Current removal localizes the mark and sends its footprint to the shared fill backend. Reverse-alpha recovery was retired. The details below preserve the historical capture rationale.

Goal: capture the Doubao "豆包AI生成" visible watermark over known flat backgrounds so we can rebuild and validate the detection silhouette used by src/remove_ai_watermarks/doubao_engine.py.

Historical findings from the capture work

Blend model: alpha compositing with a white logo watermarked = a*logo + (1-a)*original, logo = (255,255,255). Inversion: original = (watermarked - a*logo) / (1-a). Confirmed by two independent sources (an open-source remover's algorithm doc + aiwatermarkremover.dev, both say "alpha map"). One commercial blog (pixelcleanai) claims "screen blend" instead; the gray capture below settles it empirically.
Position: bottom-right corner, small margins (right ~8-20px, bottom ~5px), scales with image size. Confirmed by our sample data/fixtures/provenance/doubao-1.png (2048x2048) plus three sources.
Size scales with resolution. Third-party numbers (~90x18 at <=1024, ~180x40 at >1024) are approximate and calibrated for ~1024-1280 outputs; at 2048 the strip is much larger. A shipped third-party alpha map is only 120x20, too small for our 2K/4K target -> capture fresh.
The original implementation used reverse-alpha recovery. That path was later removed in favor of localize then fill because the latter also handles moved and re-rendered marks.

Use doubao.com specifically

The "豆包AI生成" mark is Doubao's. Jimeng / Dreamina use a different mark. Generate on doubao.com so the captured template matches our target.

How to capture (image-edit path, most reliable)

For each locally generated solid-color seed:

Open Doubao image generation, use the image-edit / reference mode, upload the seed.
Prompt (Chinese preferred): 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 (English: Recreate this image exactly as it is, keep it identical, do not add or change anything)
Download the ORIGINAL output file (not a screenshot). Do not crop / edit / re-save.

Prior art confirms uploading a pure-black image and letting Doubao stamp it works.

If edit mode is unavailable and text-to-image refuses a solid color, fall back to generating 10-12 normal-content images at one fixed resolution; the mark is the only constant across them and can be extracted by per-pixel min/median.

What to capture (priority top to bottom)

Aspect	black	white	gray128	why
1:1	3	1	1	primary alpha map + confirm the stamp is pixel-identical across runs + settle blend mode
16:9	2	1	1	anchor rule in landscape
9:16	2	1	1	anchor rule in portrait
4:3, 3:4	1 each	-	-	optional, refines anchor rule

3 blacks on 1:1: if the first two are byte-identical in the watermark region, the third is optional.
gray128 is the blend-mode test: predict the gray result from the black capture under alpha vs screen; whichever matches the real gray output is the true blend.
If the UI offers multiple output resolutions (1K / 2K / 4K), capture one black per resolution on 1:1 - needed to learn how the watermark scales.
Also grab 3-5 normal-content images on 1:1 for end-to-end removal validation.

Hygiene

Original download, never a screenshot. PNG preferred; if Doubao only gives JPEG, note it.
No crop / edit / re-save. Default settings, watermark left ON.

Committed inputs

doubao_black_1x1_1.png
doubao_gray_1x1_1.png

The black and gray captures feed scripts/visible_alpha_solve.py doubao.

Also report back

Which resolutions and aspect ratios the Doubao UI actually offers.
Whether there is a watermark on/off toggle in the UI.
Download format (PNG or JPEG).

4.1 KiB Raw Blame History