Geometry

OpenCV-compatible convex hull, minimum-area rectangle and box points — hand-ported, no opencv.js.

import { convexHull, minAreaRect, boxPoints, polygonArea, polygonPerimeter } from '@stabrise/scaledp'

type Point = [number, number]
interface RotatedRect { center: Point; size: [number, number]; angle: number }


`convexHull(points)`	Monotone chain, counter-clockwise in a y-down space
`minAreaRect(points)`	Rotating calipers; `angle` in (0, 90]
`boxPoints(rect)`	Four corners in cv2's order: BL, TL, TR, BR
`polygonArea(points)`	Shoelace, non-negative
`polygonPerimeter(points)`

These exist because the detectors' post-processing is a port of Python code that calls cv2.minAreaRect and cv2.boxPoints, and shipping opencv.js to get two functions is not a trade worth making.

Parity, and its two legitimate tolerances

test/fixtures/generate-box-goldens.py runs the real OpenCV and writes goldens; test/unit/*-parity.test.ts diffs against them. Two tolerances are encoded deliberately and should not be tightened:

1px on integer fields. cv2 computes in float32 while JavaScript is float64, so a value sitting on a .5 rounding boundary can round the other way.
angle within the shape's own symmetry group. A rectangle is invariant under a 180° rotation — 90° when square — and cv2 itself returns -0.0 or 90 for axis-aligned input depending on which hull edge its scan happens to hit.

Relationship to `Box`

minAreaRect returns a RotatedRect; the Box schema stores the same information differently — x/y as the top-left of the axis-aligned box of the same size centred on the rect's centre, width always the longer side. boxFromPolygon does that conversion.

import { boxFromPolygon, boxFromBBox } from '@stabrise/scaledp'

boxFromPolygon(quad, { text: 'hello', score: 0.98 })   // exactly 4 points
boxFromBBox([x0, y0, x1, y1], { angle: 0 })

Parity, and its two legitimate tolerances

Relationship to Box

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Relationship to `Box`