downsample static method

Uint8List downsample(Uint8List bytes, { required int width, required int height, int factor = 2, int bytesPerPixel = 1, })

Downsamples image dimensions by the given factor (e.g. 2 = half resolution).

width and height define original image dimensions. bytesPerPixel is typically 1 (grayscale) or 4 (RGBA).

Implementation

static Uint8List downsample(
  Uint8List bytes, {
  required int width,
  required int height,
  int factor = 2,
  int bytesPerPixel = 1,
}) {
  if (factor <= 1 || bytes.isEmpty) return bytes;
  final clampedFactor = factor.clamp(1, 8);
  final newWidth = (width / clampedFactor).ceil();
  final newHeight = (height / clampedFactor).ceil();
  final result = Uint8List(newWidth * newHeight * bytesPerPixel);

  int outIndex = 0;
  for (int y = 0; y < height && outIndex < result.length; y += clampedFactor) {
    for (int x = 0; x < width && outIndex < result.length; x += clampedFactor) {
      final srcIndex = (y * width + x) * bytesPerPixel;
      for (int c = 0; c < bytesPerPixel && outIndex < result.length; c++) {
        if (srcIndex + c < bytes.length) {
          result[outIndex++] = bytes[srcIndex + c];
        }
      }
    }
  }

  return Uint8List.view(result.buffer, 0, outIndex);
}