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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 | /** * Quad Tracker * * Temporal tracking for quadrilaterals across video frames. * Tracks multiple quads, calculates stability scores, and identifies * the best quad based on size, longevity, and corner stability. * * This is a pure module with no React dependencies. */ import type { DetectedQuad, Point } from './quadDetector' import { distance } from './quadDetector' // ============================================================================ // Types // ============================================================================ /** A quad being tracked across frames */ export interface TrackedQuad extends DetectedQuad { /** Unique identifier for this tracked quad */ id: string /** How many frames this quad has been detected */ frameCount: number /** Last frame number when this quad was seen */ lastSeenFrame: number /** Stability score (0-1) based on corner position variance */ stabilityScore: number /** Whether the quad is considered stable (seen enough frames) */ isStable: boolean /** Whether the quad is locked (very stable, ideal for capture) */ isLocked: boolean } /** Configuration for quad tracking */ export interface QuadTrackerConfig { /** Number of frames to track in corner history. Default: 10 */ historyLength: number /** Minimum frames to be considered "stable". Default: 3 */ minFramesForStable: number /** Minimum frames to be considered "locked". Default: 5 */ minFramesForLocked: number /** Minimum stability score (0-1) for locked state. Default: 0.5 */ minStabilityForLocked: number /** Max corner movement as fraction of diagonal to match quads. Default: 0.08 */ matchThreshold: number /** Frames a quad can be missing before removal. Default: 3 */ maxFramesMissing: number } /** Default tracker configuration */ export const DEFAULT_QUAD_TRACKER_CONFIG: QuadTrackerConfig = { historyLength: 10, minFramesForStable: 3, minFramesForLocked: 5, minStabilityForLocked: 0.5, matchThreshold: 0.08, maxFramesMissing: 3, } /** Internal tracking data for a quad */ interface TrackingData { id: string corners: [Point, Point, Point, Point] area: number aspectRatio: number frameCount: number lastSeenFrame: number stabilityScore: number cornerHistory: Array<[Point, Point, Point, Point]> } // ============================================================================ // Utility Functions // ============================================================================ /** * Check if two quads are the same based on corner positions */ function quadsMatch( q1: [Point, Point, Point, Point], q2: [Point, Point, Point, Point], frameDiagonal: number, threshold: number ): boolean { const maxDist = frameDiagonal * threshold let totalDist = 0 for (let i = 0; i < 4; i++) { totalDist += distance(q1[i], q2[i]) } return totalDist / 4 < maxDist } /** * Calculate corner stability score from position history * Lower variance = higher stability (0-1) */ function calculateCornerStability(history: Array<[Point, Point, Point, Point]>): number { if (history.length < 2) return 0 let totalVariance = 0 for (let corner = 0; corner < 4; corner++) { const xs = history.map((h) => h[corner].x) const ys = history.map((h) => h[corner].y) const meanX = xs.reduce((a, b) => a + b, 0) / xs.length const meanY = ys.reduce((a, b) => a + b, 0) / ys.length const varX = xs.reduce((a, b) => a + (b - meanX) ** 2, 0) / xs.length const varY = ys.reduce((a, b) => a + (b - meanY) ** 2, 0) / ys.length totalVariance += Math.sqrt(varX + varY) } // Convert variance to stability score // Normalize: variance of 0 = stability 1, variance of 50+ = stability 0 const avgVariance = totalVariance / 4 return Math.max(0, 1 - avgVariance / 50) } // ============================================================================ // Quad Tracker // ============================================================================ /** * Create a quad tracker instance * * @param config - Optional configuration overrides */ export function createQuadTracker(config: Partial<QuadTrackerConfig> = {}) { const cfg: QuadTrackerConfig = { ...DEFAULT_QUAD_TRACKER_CONFIG, ...config } // Internal state const trackedQuads = new Map<string, TrackingData>() let frameCount = 0 let bestQuad: TrackedQuad | null = null /** * Update tracking with newly detected quads * * @param detectedQuads - Quads detected in current frame * @param frameSize - Frame dimensions for diagonal calculation * @returns The current best quad, or null if none */ function update( detectedQuads: DetectedQuad[], frameSize: { width: number; height: number } ): TrackedQuad | null { const currentFrame = frameCount++ const frameDiagonal = Math.sqrt(frameSize.width ** 2 + frameSize.height ** 2) // Track which tracked quads were seen this frame const seenIds = new Set<string>() // Match detected quads to tracked quads for (const detected of detectedQuads) { let matched = false for (const [id, tracked] of trackedQuads) { if ( !seenIds.has(id) && quadsMatch(detected.corners, tracked.corners, frameDiagonal, cfg.matchThreshold) ) { // Update existing tracked quad tracked.corners = detected.corners tracked.area = detected.area tracked.aspectRatio = detected.aspectRatio tracked.frameCount++ tracked.lastSeenFrame = currentFrame tracked.cornerHistory.push(detected.corners) if (tracked.cornerHistory.length > cfg.historyLength) { tracked.cornerHistory.shift() } tracked.stabilityScore = calculateCornerStability(tracked.cornerHistory) seenIds.add(id) matched = true break } } if (!matched) { // New quad - start tracking const newId = `quad_${currentFrame}_${Math.random().toString(36).slice(2, 8)}` trackedQuads.set(newId, { id: newId, corners: detected.corners, area: detected.area, aspectRatio: detected.aspectRatio, frameCount: 1, lastSeenFrame: currentFrame, stabilityScore: 0, cornerHistory: [detected.corners], }) seenIds.add(newId) } } // Remove quads not seen recently for (const [id, tracked] of trackedQuads) { if (currentFrame - tracked.lastSeenFrame > cfg.maxFramesMissing) { trackedQuads.delete(id) } } // Find best quad (highest score = frameCount * stability * sqrt(area)) let best: TrackingData | null = null let bestScore = 0 for (const tracked of trackedQuads.values()) { // Only consider quads seen recently if (currentFrame - tracked.lastSeenFrame > 2) continue // Score: prioritize stability and longevity, then area const score = tracked.frameCount * (0.5 + tracked.stabilityScore) * Math.sqrt(tracked.area) if (score > bestScore) { bestScore = score best = tracked } } // Convert to TrackedQuad with status flags if (best) { const isStable = best.frameCount >= cfg.minFramesForStable const isLocked = best.frameCount >= cfg.minFramesForLocked && best.stabilityScore >= cfg.minStabilityForLocked bestQuad = { id: best.id, corners: best.corners, area: best.area, aspectRatio: best.aspectRatio, frameCount: best.frameCount, lastSeenFrame: best.lastSeenFrame, stabilityScore: best.stabilityScore, isStable, isLocked, } } else { bestQuad = null } return bestQuad } /** * Get the current best quad without processing a new frame */ function getBestQuad(): TrackedQuad | null { return bestQuad } /** * Get all currently tracked quads */ function getAllTracked(): TrackedQuad[] { const result: TrackedQuad[] = [] for (const tracked of trackedQuads.values()) { const isStable = tracked.frameCount >= cfg.minFramesForStable const isLocked = tracked.frameCount >= cfg.minFramesForLocked && tracked.stabilityScore >= cfg.minStabilityForLocked result.push({ id: tracked.id, corners: tracked.corners, area: tracked.area, aspectRatio: tracked.aspectRatio, frameCount: tracked.frameCount, lastSeenFrame: tracked.lastSeenFrame, stabilityScore: tracked.stabilityScore, isStable, isLocked, }) } return result } /** * Get current tracker statistics */ function getStats(): { trackedCount: number frameCount: number bestStability: number bestFrameCount: number } { return { trackedCount: trackedQuads.size, frameCount, bestStability: bestQuad?.stabilityScore ?? 0, bestFrameCount: bestQuad?.frameCount ?? 0, } } /** * Reset all tracking state */ function reset(): void { trackedQuads.clear() frameCount = 0 bestQuad = null } return { update, getBestQuad, getAllTracked, getStats, reset, config: cfg, } } export type QuadTracker = ReturnType<typeof createQuadTracker> |