invert method
Implementation
ContainerBuilder invert([double amount = 1.0]) => colorFilter(ColorFilter.matrix([
1 - 2 * amount, 0, 0, 0, 255 * amount,
0, 1 - 2 * amount, 0, 0, 255 * amount,
0, 0, 1 - 2 * amount, 0, 255 * amount,
0, 0, 0, 1, 0,
]));