TesseractRecognizer

Import

import { TesseractRecognizer } from '@stabrise/scaledp/ocr'

Group

Recognise

Reads

image, boxes

Writes

document

Needs

tesseract-wasm

PaddleTextRecognizer detects and recognises in a single pass, so boxes from a separate detector never reach it. This stage does the opposite: it reads exactly the boxes it is handed, cropping and straightening each one.

import { Pipeline } from '@stabrise/scaledp'
import { PdfToImage } from '@stabrise/scaledp/pdf'
import { DbnetOnnxDetector, TesseractRecognizer } from '@stabrise/scaledp/ocr'

const rows = await new Pipeline([
    new PdfToImage(),
    new DbnetOnnxDetector({ outputCol: 'boxes' }),
    new TesseractRecognizer({ inputCols: ['image', 'boxes'] }),
]).transform(file)

Document.type is 'tesseract-recognizer'. A missing box column produces a helpful OcrError in exception rather than an empty result.

boxLevel decides how fine the output boxes are

'region' is ScaleDP's behaviour: one box per region the detector found, carrying everything read inside it. Since the detectors here are line-level, so are those boxes.

'word' returns Tesseract's own word boxes instead, mapped back through the crop — padding, scaleFactor and the rotation included — so a word inside a skewed line comes back skewed the same way. Python has no equivalent; the words were always in the response, only their geometry was being discarded.

onlyRotated defaults the other way from Python

ScaleDP defaults it to true, because there the stage refines an OCR pass that already ran and skipping upright boxes is the whole point. Standalone it is the primary recognizer, and that default would return an empty document for the ordinary detector-then-recognize pipeline.

Set it to true to use the stage as a fix-up pass over boxes that already carry text.

Straightening

The crop is a perspective warp onto the box's own axes, verified readable end to end at 0, +25 and −18 degrees. Recognition quality on skewed text is then bounded by the detector: a box whose reported angle does not match the text's produces a crop that is still skewed.

padding defaults to 5, which is what ScaleDP hardcodes. scaleFactor resizes the page before cropping — useful for small text — and coordinates are divided back out, so the boxes stay in the page's own space.

detectLineOrientation classifies each crop 0°/180° and turns the inverted ones before reading, using the same ~9 MB model as LineOrientationDetector.

Parameters