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No content changes: git diff --ignore-all-space over these files is empty. The churn came from editing on Windows against a repo checked out with LF.
113 lines
4.0 KiB
Dart
113 lines
4.0 KiB
Dart
import 'dart:io';
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import 'package:flutter/foundation.dart';
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import 'package:image/image.dart' as img;
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class BlurResult {
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final double score; // Scaled score (0 - 100)
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final bool isBlur;
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final double rawScore;
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BlurResult({required this.score, required this.isBlur, required this.rawScore});
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}
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class BlurDetector {
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static BlurResult? mockResult;
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/// We scale the raw variance of Laplacian score (0 - 500.0) to a scaled score (0 - 100.0).
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/// Center cropping and Gaussian blur isolate text sharpness.
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static const double maxRawScore = 500.0;
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static const double rawThreshold = 400.0; // Below this raw score is blurry (80% of 500.0)
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static const double scaledThreshold = 80.0; // Corresponding scaled threshold (400 / 500 * 100)
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static Future<BlurResult> checkBlur(String filePath) async {
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if (mockResult != null) {
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return mockResult!;
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}
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return await compute(_checkBlurIsolate, filePath);
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}
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static BlurResult _checkBlurIsolate(String filePath) {
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try {
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final bytes = File(filePath).readAsBytesSync();
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final image = img.decodeImage(bytes);
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if (image == null) {
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return BlurResult(score: 0, isBlur: true, rawScore: 0);
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}
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// 1. Resize to 300 width for fast calculation (reduces isolate time to <100ms)
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final resized = img.copyResize(image, width: 300);
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// 2. Crop the center 60% area to focus purely on text and ignore document borders / backgrounds
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final cropWidth = (resized.width * 0.60).toInt();
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final cropHeight = (resized.height * 0.60).toInt();
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final startX = (resized.width - cropWidth) ~/ 2;
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final startY = (resized.height - cropHeight) ~/ 2;
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final cropped = img.copyCrop(resized, x: startX, y: startY, width: cropWidth, height: cropHeight);
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// 3. Apply Gaussian Blur to filter out sensor noise/camera shaking noise
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final smoothed = img.gaussianBlur(cropped, radius: 1);
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// 4. Convert to Grayscale
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final gray = img.grayscale(smoothed);
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final width = gray.width;
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final height = gray.height;
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// 5. Compute Laplacian values
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final laplacianValues = <double>[];
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double sum = 0.0;
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for (int y = 1; y < height - 1; y++) {
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for (int x = 1; x < width - 1; x++) {
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final p = gray.getPixel(x, y);
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final pLeft = gray.getPixel(x - 1, y);
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final pRight = gray.getPixel(x + 1, y);
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final pTop = gray.getPixel(x, y - 1);
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final pBottom = gray.getPixel(x, y + 1);
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// Get grayscale values directly (r = g = b)
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final lum = p.r.toDouble();
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final lumLeft = pLeft.r.toDouble();
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final lumRight = pRight.r.toDouble();
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final lumTop = pTop.r.toDouble();
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final lumBottom = pBottom.r.toDouble();
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// 3x3 Laplacian: 4 * center - left - right - top - bottom
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final laplacian = (4 * lum) - lumLeft - lumRight - lumTop - lumBottom;
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laplacianValues.add(laplacian);
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sum += laplacian;
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}
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}
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final count = laplacianValues.length;
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if (count == 0) return BlurResult(score: 0, isBlur: true, rawScore: 0);
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final mean = sum / count;
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// 6. Calculate Variance of Laplacian
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double varianceSum = 0.0;
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for (final val in laplacianValues) {
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varianceSum += (val - mean) * (val - mean);
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}
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final rawScore = varianceSum / count;
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// 7. Scale score to 0-100 range
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final scaledScore = (rawScore / maxRawScore * 100).clamp(0.0, 100.0);
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final isBlur = scaledScore < scaledThreshold;
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debugPrint('Blur detection: Raw Score: $rawScore, Scaled Score: $scaledScore, IsBlur: $isBlur');
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return BlurResult(
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score: scaledScore,
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isBlur: isBlur,
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rawScore: rawScore,
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);
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} catch (e) {
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debugPrint('Error detecting blur in isolate: $e');
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return BlurResult(score: 0, isBlur: true, rawScore: 0);
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}
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}
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}
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