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[object Object] BOOKSCANNER

Pipeline processing

Pipeline processing is the second stage of the chain (after import, before OCR and export). It is the heart of Aglaïa: an ordered list of processors, each transforming an image and passing it on, until a raw scan becomes a clean, straight, readable page. The same pipeline runs in the capture GUI and in headless CLI batches, so what you see on screen is exactly what a script produces.

Background

A scanned page needs several independent corrections — exposure, skew, curvature, thresholding — and the right order matters: you deskew before you dewarp, dewarp before you binarize, binarize before you OCR. Aglaïa models this as a chain of small, single-purpose processors rather than one monolithic function, so each step can be tuned, reordered, profiled, or swapped on its own.

A pipeline is just a YAML file: an ordered list of steps, each naming a processor and its options. The chain runs across multiple worker processes and persists every intermediate result to the SQLite-backed project file so you can inspect, branch, and replay.

Use cases

  • Tune one stage — raise the binarizer’s window size or disable twist in the dewarper without touching any other step.
  • Branch the output — a page-detection step can emit several child crops that each re-enter the pipeline independently (e.g. the two halves of an open spread).
  • Reorder or swap — drop in a different binarizer, or move deskew before page detection, by editing the YAML.
  • Batch a shelf — point the headless CLI at a folder and let the same pipeline run unattended.

Persistence and branching

Each step’s output is stored as a node in the project’s node tree; a branch-emitting step (page detection) forks the tree, and the user picks the chosen output per branch — that choice is what OCR and export consume. A step’s heavy image can be dropped (persist: false) and rebuilt on demand by the replay pass, which recomposes the page from the nearest stored image with the fewest interpolations — so a page can be replayed from any point without re-capturing it.