宽色域 Color 的迁移指南

// Before: Constructing an sRGB color from the lower 8 bits of four integers.
final magenta = Color.fromARGB(0xff, 0xff, 0x0, 0xff);

// After: Constructing a color with normalized floating-point components.
final magenta = Color.from(alpha: 1.0, red: 1.0, green: 0.0, blue: 1.0);

class Foo implements Color {
  int _red;

  @override
  double get r => _red / 255.0;
}

// Before
double redRatio(Color x, Color y) => x.red / y.red;

// After
double redRatio(Color x, Color y) {
  final xPrime = x.withValues(colorSpace: ColorSpace.extendedSRGB);
  final yPrime = y.withValues(colorSpace: ColorSpace.extendedSRGB);
  return xPrime.r / yPrime.r;
}

extension IntColorComponents on Color {
  int get intAlpha => _floatToInt8(this.a);
  int get intRed => _floatToInt8(this.r);
  int get intGreen => _floatToInt8(this.g);
  int get intBlue => _floatToInt8(this.b);

  int _floatToInt8(double x) {
    return (x * 255.0).round() & 0xff;
  }
}

// Prints 0.5019607843137255.
print(Colors.black.withOpacity(0.5).a);
// Prints 0.5.
print(Colors.black.withValues(alpha: 0.5).a);

// Before: Access the alpha channel as a (converted) floating-point value.
final x = color.opacity;

// After: Access the alpha channel directly.
final x = color.a;

// Before: Create a new color with the specified opacity.
final x = color.withOpacity(0.0);

// After: Create a new color with the specified alpha channel value,
// accounting for the current or specified color space.
final x = color.withValues(alpha: 0.0);

// Before: Check exact equality of int-based color.
expect(calculateColor(), const Color(0xffff00ff));

// After: Check rough equality of floating-point-based color.
expect(calculateColor(), isSameColorAs(const Color(0xffff00ff)));