getSizeAsync method

@override Future<Size> getSizeAsync(AsyncImageInput input)

Returns the size of the input.

Implementation

@override
Future<Size> getSizeAsync(AsyncImageInput input) async {
  int start = 2;
  BlockEntity? block;
  var orientation = 1;

  while (true) {
    block = await _getBlockAsync(input, start);

    if (block == null) {
      throw Exception('Invalid jpeg file');
    }

    if (block.type == 0xE1) {
      final app1BlockData = await input.getRange(
        start,
        block.start + block.length,
      );
      final exifOrientation = _getOrientation(app1BlockData);
      if (exifOrientation != null) {
        orientation = exifOrientation;
      }
    }

    if (block.type == 0xC0 || block.type == 0xC2) {
      final widthList = await input.getRange(start + 7, start + 9);
      final heightList = await input.getRange(start + 5, start + 7);
      orientation = (await input.getRange(start + 9, start + 10))[0];
      return _getSize(widthList, heightList, orientation);
    } else {
      start += block.length;
    }
  }
}