creek

 1import 'dart:typed_data';
 2import 'dart:io';
 3import 'package:image/image.dart' as img;
 4
 5class ClipImageProcessor {
 6  // CLIP Standard Constants
 7  static const List<double> mean = [0.48145466, 0.4578275, 0.40821073];
 8  static const List<double> std = [0.26862954, 0.26130258, 0.27577711];
 9
10  /// Reads file, resizes, crops, normalizes, and returns Float32List [1, 3, 224, 224]
11  static Future<Float32List?> preprocess(String filePath) async {
12    final bytes = await File(filePath).readAsBytes();
13    final image = img.decodeImage(bytes);
14
15    if (image == null) return null;
16
17    // 1. Resize (Shortest side to 224)
18    int w = image.width;
19    int h = image.height;
20    int target = 224;
21
22    img.Image resized;
23    if (w < h) {
24      resized = img.copyResize(image, width: target);
25    } else {
26      resized = img.copyResize(image, height: target);
27    }
28
29    // 2. Center Crop (224x224)
30    final cropped = img.copyResizeCropSquare(resized, size: target);
31
32    // 3. Convert to Float32 List (NCHW format: Batch, Channels, Height, Width)
33    // Size: 1 * 3 * 224 * 224 = 150,528 float values
34    final Float32List inputData = Float32List(1 * 3 * 224 * 224);
35
36    int pixelIndex = 0;
37    // Iterate pixels and separate channels
38    // Planar format (RRRR... GGGG... BBBB...)
39    int rOffset = 0;
40    int gOffset = 224 * 224;
41    int bOffset = 224 * 224 * 2;
42
43    for (var y = 0; y < 224; y++) {
44      for (var x = 0; x < 224; x++) {
45        final pixel = cropped.getPixel(x, y);
46
47        // Normalize: (Value/255 - Mean) / Std
48        double r = (pixel.r / 255.0 - mean[0]) / std[0];
49        double g = (pixel.g / 255.0 - mean[1]) / std[1];
50        double b = (pixel.b / 255.0 - mean[2]) / std[2];
51
52        inputData[rOffset + pixelIndex] = r;
53        inputData[gOffset + pixelIndex] = g;
54        inputData[bOffset + pixelIndex] = b;
55
56        pixelIndex++;
57      }
58    }
59
60    return inputData;
61  }
62}