lerp method

Color lerp (Color a, Color b, double t)

Linearly interpolate between two colors.

This is intended to be fast but as a result may be ugly. Consider HSVColor or writing custom logic for interpolating colors.

If either color is null, this function linearly interpolates from a transparent instance of the other color. This is usually preferable to interpolating from material.Colors.transparent (const Color(0x00000000)), which is specifically transparent black.

The t argument represents position on the timeline, with 0.0 meaning that the interpolation has not started, returning a (or something equivalent to a), 1.0 meaning that the interpolation has finished, returning b (or something equivalent to b), and values in between meaning that the interpolation is at the relevant point on the timeline between a and b. The interpolation can be extrapolated beyond 0.0 and 1.0, so negative values and values greater than 1.0 are valid (and can easily be generated by curves such as Curves.elasticInOut). Each channel will be clamped to the range 0 to 255.

Values for t are usually obtained from an Animation<double>, such as an AnimationController.

Implementation

static Color lerp(Color a, Color b, double t) {
  assert(t != null);
  if (a == null && b == null)
    return null;
  if (a == null)
    return _scaleAlpha(b, t);
  if (b == null)
    return _scaleAlpha(a, 1.0 - t);
  return Color.fromARGB(
    lerpDouble(a.alpha, b.alpha, t).toInt().clamp(0, 255),
    lerpDouble(a.red, b.red, t).toInt().clamp(0, 255),
    lerpDouble(a.green, b.green, t).toInt().clamp(0, 255),
    lerpDouble(a.blue, b.blue, t).toInt().clamp(0, 255),
  );
}