54 lines
1.9 KiB
Dart
54 lines
1.9 KiB
Dart
import 'dart:typed_data';
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import '../detection/detection_result.dart';
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import '../detection/motion_aggregator.dart';
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/// 轻量运动检测：相邻帧 Y 通道差分 + 分块聚合。
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/// 小尺寸工作（约 128x128 内），在分析流中串行调用。
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/// 相机大幅移动时（全屏帧差）自动忽略本帧，避免误报。
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class MotionDetector {
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final int maxWidth;
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final int maxHeight;
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List<int>? _prevGray;
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MotionDetector({this.maxWidth = 128, this.maxHeight = 128});
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/// 后台 isolate 用原始数据接口（不依赖 CameraImage）。
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List<MotionRegion> detectMotionRaw(
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Uint8List yPlane, int yStride, int width, int height) {
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final w = width, h = height;
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final scale = maxWidth / w < maxHeight / h ? maxWidth / w : maxHeight / h;
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final tw = (w * scale).toInt().clamp(1, maxWidth);
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final th = (h * scale).toInt().clamp(1, maxHeight);
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if (tw == 0 || th == 0) return const [];
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// 取 Y 平面缩放灰度（最近邻下采样到 128x128 内）
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final y = yPlane;
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final gray = List<int>.filled(tw * th, 0);
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for (var oy = 0; oy < th; oy++) {
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final sy = (oy / scale).toInt().clamp(0, h - 1);
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for (var ox = 0; ox < tw; ox++) {
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final sx = (ox / scale).toInt().clamp(0, w - 1);
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gray[oy * tw + ox] = y[sy * yStride + sx];
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}
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}
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final prev = _prevGray;
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_prevGray = List.of(gray);
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if (prev == null || prev.length != gray.length) return const [];
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final diff = MotionAggregator.diffMask(gray, prev);
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final motionTotal = diff.fold(0, (a, b) => a + b);
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// 全屏大差异 → 相机移动/大范围变化，忽略本帧
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if (motionTotal > tw * th / 2) return const [];
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if (motionTotal < 12) return const [];
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return MotionAggregator.aggregate(diff, tw, th);
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}
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/// 相机切换后重置参考帧，避免旧帧误差
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void reset() {
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_prevGray = null;
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}
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}
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