97 lines
3.2 KiB
Dart
97 lines
3.2 KiB
Dart
import 'dart:math' as math;
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import 'detection_result.dart';
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/// 帧差运动聚合：每像素 0/1 差分掩码 → 8x8 分块统计 → 连通块聚合为运动区域。
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class MotionAggregator {
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static const int blockGrid = 8;
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static const double blockActiveRatio = 0.30;
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static const int maxRegions = 3;
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static const int diffThreshold = 25;
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static List<MotionRegion> aggregate(List<int> diff, int width, int height) {
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final bw = width ~/ blockGrid;
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final bh = height ~/ blockGrid;
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if (bw == 0 || bh == 0) return const [];
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final active = List<bool>.filled(blockGrid * blockGrid, false);
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for (var by = 0; by < blockGrid; by++) {
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for (var bx = 0; bx < blockGrid; bx++) {
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final blockW = bx == blockGrid - 1 ? width - bx * bw : bw;
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final blockH = by == blockGrid - 1 ? height - by * bh : bh;
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var motion = 0;
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for (var y = by * bh; y < by * bh + blockH; y++) {
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var idx = y * width + bx * bw;
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for (var x = 0; x < blockW; x++) {
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motion += diff[idx + x];
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}
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idx += width;
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}
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active[by * blockGrid + bx] =
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motion > blockW * blockH * blockActiveRatio;
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}
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}
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final regions = <MotionRegion>[];
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final visited = List<bool>.filled(active.length, false);
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for (var i = 0; i < active.length; i++) {
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if (!active[i] || visited[i]) continue;
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var minX = blockGrid, minY = blockGrid, maxX = -1, maxY = -1;
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final stack = <int>[i];
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visited[i] = true;
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while (stack.isNotEmpty) {
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final cur = stack.removeLast();
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final bx = cur % blockGrid;
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final by = cur ~/ blockGrid;
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if (bx < minX) minX = bx;
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if (bx > maxX) maxX = bx;
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if (by < minY) minY = by;
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if (by > maxY) maxY = by;
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for (final nb in neighbors(cur)) {
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if (active[nb] && !visited[nb]) {
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visited[nb] = true;
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stack.add(nb);
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}
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}
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}
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if (maxX - minX > 3 || maxY - minY > 3) continue; // 全屏噪声过滤
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regions.add(MotionRegion(
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minX * bw / width,
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minY * bh / height,
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math.min((maxX + 1) * bw, width) / width,
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math.min((maxY + 1) * bh, height) / height,
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));
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if (regions.length >= maxRegions) break;
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}
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return regions;
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}
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static List<int> neighbors(int i) {
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final bx = i % blockGrid;
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final by = i ~/ blockGrid;
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final list = <int>[];
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if (bx > 0) list.add(i - 1);
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if (bx < blockGrid - 1) list.add(i + 1);
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if (by > 0) list.add(i - blockGrid);
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if (by < blockGrid - 1) list.add(i + blockGrid);
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return list;
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}
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/// 检测框中心是否落在运动区域内（用于置信度提升判定）
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static bool centerInRegion(DetectionResult box, MotionRegion region) =>
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box.centerX >= region.left &&
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box.centerX <= region.right &&
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box.centerY >= region.top &&
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box.centerY <= region.bottom;
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/// 帧差掩码：|g - prev| > threshold → 1
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static List<int> diffMask(List<int> gray, List<int> prev,
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[int threshold = diffThreshold]) {
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final diff = List<int>.filled(gray.length, 0);
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for (var i = 0; i < gray.length; i++) {
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diff[i] = (gray[i] - prev[i]).abs() > threshold ? 1 : 0;
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}
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return diff;
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}
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}
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