a property

num a

@override
num get a => palette == null
    ? numChannels == 2
        ? data[_index + 1]
        : numChannels > 3
            ? data[_index + 3]
            : 255
    : palette!.getAlpha(data[_index]);

void a=(num a)

@override
set a(num a) {
  if (numChannels == 2) {
    data[_index + 1] = a.clamp(0, 255).toInt();
  } else if (image.numChannels > 3) {
    data[_index + 3] = a.clamp(0, 255).toInt();
  }
}