3 · Registration
Click the centres of the sheet's four corner marks — the ones out in the page
margin, which every sheet carries whether or not it is full.
Every frame is then placed by geometry: the cell positions are known exactly from the config, and
a flat sheet maps to the photo by one perspective transform. No pixels are read, so collage,
add-ons and uneven washes cannot throw it off.
Adjusting individual frames
Drag any corner to nudge it, or select one with
1–4 and arrow-key it (shift = 10 px). Step frames with
, / . Press C to clear a frame and re-place its corners by
clicking — each click lands on the next corner, and the ring shows which one is coming.
Every frame you nudge feeds a least-squares fit of the whole page, which re-places
the frames you have not touched. Useful when a wide lens makes the sheet drift at the edges.
5 · Export
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MP4 uses ffmpeg.wasm, served from this site. WebM and the PNG sequence work offline too.
6 · Debug
A zip of the state, the config, the scan as drawn, and a contact sheet of every
frame — so the exact thing you are looking at can be handed over.