remove-ai-watermarks/data/doubao_capture

Doubao visible watermark capture

Status (completed 2026-05-29): the capture described below was carried out (black + gray Doubao captures) and the exact alpha map was solved. Removal is now reverse-alpha only: at the captured native width recovery is pixel-exact and inpaint is OFF; a residual inpaint runs off-native only. See the doubao_engine.py notes in the root CLAUDE.md. The text below is kept as the historical capture plan.

Goal: capture the Doubao "豆包AI生成" visible watermark over known flat backgrounds so we can build a per-pixel alpha map and a reverse-alpha-blend remover, the same way the Gemini sparkle engine works (src/remove_ai_watermarks/gemini_engine.py).

What we already know (verified from prior art, 2026-05-26)

• 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/samples/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 planning assumption was that clean inversion leaves residue on textured backgrounds, so the remover would pair the alpha map with inpainting. After the capture this turned out unnecessary at the native width (recovery is pixel-exact there and inpaint is off); the shipped remover is reverse-alpha only, with a residual inpaint applied off-native only.

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 seed in seeds/:

1. Open Doubao image generation, use the image-edit / reference mode, upload the seed.
2. 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)
3. 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.

Naming, drop into captures/

doubao_black_1x1_1.png
doubao_white_1x1_1.png
doubao_gray128_1x1_1.png
doubao_black_16x9_1.png
doubao_content_1x1_1.png

Also report back

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