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API

API Details

Objects

The library provides an object-oriented API that maps to OpenCV structures. Each object has specific properties, methods, and static methods for creation.

Mat

The core multidimensional array used to store images and matrices.

Properties:

  • type: ObjectType.Mat
  • rows: number (Read-only)
  • cols: number (Read-only)

Methods:

  • release(): void - Frees the memory allocated for the Mat.
  • toBase64(): string - Returns a base64 encoded string of the Mat (default format: JPEG).
  • toBuffer(type: 'uint8' | 'uint16' | 'uint32' | 'int8' | 'int16' | 'int32' | 'float32' | 'float64') - Converts the Mat to a TypedArray, returning { cols: number, rows: number, channels: number, buffer: TypedArray }.
  • saveToFile(path: string): void - Saves the Mat to the specified local file path.

Static Methods:

  • Mat.create(rows?: number, cols?: number, dataType?: DataTypes, data?: number[]): Mat
  • Mat.createFromBase64(base64: string): Mat
  • Mat.createFromBuffer(type: string, rows: number, cols: number, channels: number, buffer: TypedArray): Mat
  • Mat.createFromVisionCameraFrameBuffer(rows: number, cols: number, channels: number, input: Uint8Array): Mat

MatVector

A vector (array) of Mat objects.

Properties:

  • type: ObjectType.MatVector
  • length: number (Read-only)

Methods:

  • release(): void - Frees the memory allocated for the MatVector.
  • get(index: number): Mat - Returns the Mat at the specified index.
  • push(item: Mat): void - Adds a Mat to the vector.

Static Methods:

  • MatVector.create(): MatVector

Point

Represents a 2D point with integer coordinates.

Properties:

  • type: ObjectType.Point
  • x: number
  • y: number

Methods:

  • release(): void - Frees the memory allocated for the Point.

Static Methods:

  • Point.create(x: number, y: number): Point

PointVector

A vector of Point objects.

Properties:

  • type: ObjectType.PointVector
  • length: number (Read-only)

Methods:

  • release(): void - Frees the memory allocated for the vector.
  • get(index: number): Point - Returns the Point at the specified index.
  • push(item: Point): void - Adds a Point to the vector.
  • getAll(): Point[] - Returns a JS array of all points.

Static Methods:

  • PointVector.create(): PointVector

Point2f

Represents a 2D point with floating-point coordinates.

Properties:

  • type: ObjectType.Point2f
  • x: number
  • y: number

Methods:

  • release(): void

Static Methods:

  • Point2f.create(x: number, y: number): Point2f

Point2fVector

A vector of Point2f objects.

Properties:

  • type: ObjectType.Point2fVector
  • length: number (Read-only)

Methods:

  • release(): void
  • get(index: number): Point2f
  • push(item: Point2f): void
  • getAll(): Point2f[]

Static Methods:

  • Point2fVector.create(points?: Point2f[]): Point2fVector

PointVectorOfVectors

A vector of PointVector objects. Typically used for holding contours.

Properties:

  • type: ObjectType.PointVectorOfVectors
  • length: number (Read-only)

Methods:

  • release(): void
  • get(index: number): PointVector
  • push(item: PointVector): void
  • getAll(): PointVector[]

Static Methods:

  • PointVectorOfVectors.create(): PointVectorOfVectors

Rect

Represents a 2D rectangle.

Properties:

  • type: ObjectType.Rect
  • x: number
  • y: number
  • width: number
  • height: number

Methods:

  • release(): void

Static Methods:

  • Rect.create(x: number, y: number, width: number, height: number): Rect

RectVector

A vector of Rect objects.

Properties:

  • type: ObjectType.RectVector
  • length: number (Read-only)

Methods:

  • release(): void
  • get(index: number): Rect
  • push(item: Rect): void
  • getAll(): Rect[]

Static Methods:

  • RectVector.create(): RectVector

Size

Represents the size of an image or rectangle.

Properties:

  • type: ObjectType.Size
  • width: number
  • height: number

Methods:

  • release(): void

Static Methods:

  • Size.create(width: number, height: number): Size

Vec3b

Represents a 3-element vector, typically used for storing colors.

Properties:

  • type: ObjectType.Vec3b
  • a: number
  • b: number
  • c: number

Methods:

  • release(): void

Static Methods:

  • Vec3b.create(): Vec3b

Scalar

Represents a 4-element vector, often used for representing colors (e.g. RGBA).

Properties:

  • type: ObjectType.Scalar
  • a: number
  • b: number
  • c: number
  • d: number

Methods:

  • release(): void

Static Methods:

  • Scalar.create(a: number, b?: number, c?: number, d?: number): Scalar

RotatedRect

Represents a rotated rectangle.

Properties:

  • type: ObjectType.RotatedRect
  • x: number - center x coordinate
  • y: number - center y coordinate
  • width: number - full width of the rotated rectangle
  • height: number - full height of the rotated rectangle
  • angle: number - rotation angle in degrees

Methods:

  • release(): void

Static Methods:

  • RotatedRect.create(): RotatedRect

TermCriteria

Defines termination criteria for iterative algorithms.

Properties:

  • type: ObjectType.TermCriteria
  • maxCount: number
  • epsilon: number

Methods:

  • release(): void

Static Methods:

  • TermCriteria.create(termCriteriaType: TermCriteriaType, maxCount: number, epsilon: number): TermCriteria

ORB

An ORB (Oriented FAST and Rotated BRIEF) feature detector. Created by OpenCV.ORB_create(...) and passed to OpenCV.detectAndCompute. It is an opaque handle with no readable properties.

Properties:

  • type: ObjectType.ORB

Methods:

  • release(): void

There is no ORB.create() static method — use the OpenCV.ORB_create(...) function instead.

BFMatcher

A brute-force descriptor matcher. Created by OpenCV.BFMatcher_create(...) and passed to OpenCV.matchBF / OpenCV.knnMatchBF. It is an opaque handle with no readable properties.

Properties:

  • type: ObjectType.BFMatcher

Methods:

  • release(): void

There is no BFMatcher.create() static method — use the OpenCV.BFMatcher_create(...) function instead.

KeyPointVector

A vector of keypoints returned by OpenCV.detectAndCompute. A keypoint is exposed as plain JS data: { x, y, size, angle, response, octave, classId }.

Properties:

  • type: ObjectType.KeyPointVector
  • length: number (Read-only)

Methods:

  • release(): void
  • get(index: number): KeyPoint - Returns the keypoint at the given index.
  • toArray(): KeyPoint[] - Returns all keypoints as a plain array.

DMatchVector

A vector of descriptor matches returned by OpenCV.matchBF. A match is exposed as plain JS data: { queryIdx, trainIdx, imgIdx, distance }.

Properties:

  • type: ObjectType.DMatchVector
  • length: number (Read-only)

Methods:

  • release(): void
  • get(index: number): DMatch - Returns the match at the given index.
  • toArray(): DMatch[] - Returns all matches as a plain array.

DMatchVectorVector

A vector of vectors of descriptor matches returned by OpenCV.knnMatchBF. get(i) returns the array of the k best matches for the i-th query descriptor.

Properties:

  • type: ObjectType.DMatchVectorVector
  • length: number (Read-only)

Methods:

  • release(): void
  • get(index: number): DMatch[] - Returns the k best matches for the given query index.
  • toArray(): DMatch[][] - Returns all match groups as a plain nested array.

OpenCV Module

General Functions

Functions from the OpenCV library are directly attached to the exported OpenCV instance. Instead of the previous generic invoke() method, you call functions directly with type-safety.

import { OpenCV } from 'react-native-fast-opencv';
 
const src1 = Mat.create();
const src2 = Mat.create();
const dst = Mat.create();
 
// Direct invocation of OpenCV function
OpenCV.absdiff(src1, src2, dst);
 
// ...
src1.release();
src2.release();
dst.release();

For a full list of available OpenCV functions, refer to the Available OpenCV Functions section.

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UsageAvailable OpenCV functions