contrast method

ContainerBuilder contrast(
  1. double value
)

Implementation

ContainerBuilder contrast(double value) {
  final factor = (259 * (value * 255 + 255)) / (255 * (259 - value * 255));
  return colorFilter(ColorFilter.matrix([
    factor, 0, 0, 0, 128 * (1 - factor),
    0, factor, 0, 0, 128 * (1 - factor),
    0, 0, factor, 0, 128 * (1 - factor),
    0, 0, 0, 1, 0,
  ]));
}