hand_detection_native library

Native (non-web) entry point for hand_detection.

Import this library on mobile and desktop targets that need access to native-only symbols (e.g. HandDetectorIsolate, Accelerator, Precision) that are intentionally absent from the default conditional-export entry (package:hand_detection/hand_detection.dart), which defaults to the web library so the package scores WASM-ready.

Classes

BoundingBox

An axis-aligned or rotated bounding box defined by four corner points.

CameraFrame

A camera frame packaged for off-thread colour conversion and inference.

CameraHandOverlayPainter

Paints hand detection results over a live camera preview.

FpsCounter

A simple 1-second rolling FPS counter for camera-preview apps.

GestureResult

Result of gesture recognition containing the detected gesture and confidence.

Hand

Detected hand with bounding box and optional landmarks.

HandDetectionDart

Dart plugin registration for hand_detection.

HandDetector

On-device hand detection and landmark estimation using TensorFlow Lite.

HandDetectorIsolate

Deprecated: Use HandDetector instead.

HandLandmark

A single keypoint with 3D coordinates and visibility score.

HandLandmarks

Collection of hand landmarks with confidence score (internal use).

LetterboxParams

Parameters for aspect-preserving resize with centered padding.

MultiOverlayPainter

Paints hand detection results over a still image.

PackedYuv

A contiguous YUV buffer produced by packYuv420, ready to hand to a native colour-conversion routine.

PalmDetection

A detected palm with rotation rectangle parameters.

PerformanceConfig

Configuration for interpreter hardware acceleration and threading.

Point

A point with x, y, and optional z coordinates.

Enums

Accelerator

Hardware accelerator requested for LiteRT Next compilation.

CameraFrameConversion

The colour conversion a CameraFrame's bytes need before being used as a 3-channel BGR image. Detector packages map this to an opencv COLOR_* code at the point of decode, inside their existing detection isolate.

CameraFrameRotation

Optional rotation applied after colour conversion. Detector packages map this to an opencv ROTATE_* code.

GestureType

Recognized hand gesture types from MediaPipe gesture classifier.

Handedness

Handedness type indicating left or right hand.

HandLandmarkModel

Hand landmark model variant for landmark extraction.

HandLandmarkType

Hand landmark types for the MediaPipe hand landmark model.

HandMode

Detection mode controlling the two-stage pipeline behavior.

PerformanceMode

Hardware acceleration mode for LiteRT inference.

Precision

GPU precision mode for LiteRT Next compilation.

YuvLayout

Memory layout of a packed YUV buffer produced by packYuv420.

Constants

handLandmarkConnections → const List<List<HandLandmarkType>>

Defines the standard skeleton connections between hand landmarks.

numHandLandmarks → const int

Number of hand landmarks (21 for MediaPipe hand model).

Functions

allocTensorShape(List<int> shape) → Object

Allocates a nested list structure matching the given tensor shape.

barQuarterTurns(DeviceOrientation orientation) → int

Quarter-turns (clockwise) to rotate a top-bar widget so it reads upright when the device is in landscape. Use with RotatedBox(quarterTurns: ...).

bgrBytesToRgbFloat32({required Uint8List bytes, required int totalPixels, Float32List? buffer}) → Float32List

Converts BGR bytes to a flat Float32List with 0.0..1.0 normalization.

bgrBytesToSignedFloat32({required Uint8List bytes, required int totalPixels, Float32List? buffer}) → Float32List

Converts BGR bytes to a flat Float32List with -1.0..1.0 normalization.

clamp01(double v) → double

Clamps v to the range 0.0..1.0. Returns 0.0 for NaN inputs.

clip(double v, double lo, double hi) → double

Clamps v to the range lo..hi.

computeLetterboxParams({required int srcWidth, required int srcHeight, required int targetWidth, required int targetHeight, bool roundDimensions = true}) → LetterboxParams

Computes letterbox parameters for resizing srcWidthxsrcHeight to fit within targetWidthxtargetHeight while preserving aspect ratio.

coverFitScaleOffset(int sourceW, int sourceH, double viewW, double viewH) → ({double offsetX, double offsetY, double scale})

Cover-fit scale + offset for rendering a source region of size (sourceW, sourceH) into a viewport of size (viewW, viewH).

createNHWCTensor4D(int height, int width) → List<List<List<List<double>>>>

Creates a pre-allocated [1][height][width][3] tensor structure.

detectionSize({required int width, required int height, required CameraFrameRotation? rotation, required int maxDim}) → Size

Compute the final detection-image size used by overlay painters to map detector coordinates back onto the widget coord space.

drawBoundingBoxOutline({required Canvas canvas, required BoundingBox bbox, required double scaleX, required double scaleY, required double offsetX, required double offsetY, required Paint paint}) → void

Draw the axis-aligned outline of a BoundingBox transformed by a linear scale + offset. Use a stroked Paint for an outline, or a filled one to tint the interior.

drawLandmarkMarker(Canvas canvas, double x, double y, {double glowRadius = 8, double pointRadius = 5, double centerRadius = 2, Paint? glowPaint, Paint? pointPaint, Paint? centerPaint}) → void

Draw a standard "glow + point + center dot" triple-circle landmark marker at (x, y) in canvas coordinates.

drawSkeletonConnections({required Canvas canvas, required List<Offset> scaledPoints, required List<(int, int)> connections, required Paint paint}) → void

Draw straight-line connections between pre-scaled landmark points.

fillNHWC4D(Float32List flat, List<List<List<List<double>>>> cache, int inH, int inW) → void

Fills an NHWC 4D tensor cache from a flat Float32List.

flattenDynamicTensor(Object? out) → Float32List

Flattens an arbitrarily nested tensor to a flat Float32List.

getRotatedRectPoints(double cx, double cy, double width, double height, double rotation) → List<Offset>

Calculates the 4 corner points of a rotated rectangle.

packYuv420({required int width, required int height, required YuvPlane y, required YuvPlane u, YuvPlane? v, Uint8List? into}) → PackedYuv?

Packs a YUV420 camera frame into a single contiguous buffer suitable for native colour conversion (e.g. opencv's cvtColor with a COLOR_YUV2BGR_NV21 / COLOR_YUV2BGR_NV12 / COLOR_YUV2BGR_I420 code).

prepareCameraFrame({required int width, required int height, required List<CameraPlane> planes, CameraFrameRotation? rotation, bool isBgra = true}) → CameraFrame?

Prepare a CameraFrame descriptor from raw camera planes, for use with a detector package's detectFromCameraFrame(...) method.

prepareCameraFrameFromImage(Object cameraImage, {CameraFrameRotation? rotation, bool? isBgra}) → CameraFrame?

Convenience wrapper around prepareCameraFrame that accepts any object duck-typed to package:camera's CameraImage (i.e. exposing width, height, and a planes iterable of objects with bytes, bytesPerRow, and bytesPerPixel getters).

rotationForFrame({required int width, required int height, required int sensorOrientation, required bool isFrontCamera, required DeviceOrientation deviceOrientation}) → CameraFrameRotation?

Compute the rotation needed to present a camera frame upright to an on-device detection model, given the camera's sensor orientation and the device's current physical orientation.

sigmoid(double x) → double

Sigmoid activation function.

sigmoidClipped(double x, {double limit = 80.0}) → double

Sigmoid with input clipping to prevent overflow.

Typedefs

CameraPlane = ({Uint8List bytes, int pixelStride, int rowStride})

A single camera frame plane exposed by a camera plugin.

YuvPlane = ({Uint8List bytes, int pixelStride, int rowStride})

A single YUV plane exposed by a camera plugin, decoupled from any specific Flutter plugin's type (e.g. CameraImage.Plane).