interpolate package

Sometimes you need to map value from one range to another. This is where you should use interpolate functions which approximates values between points in the output range and lets you map value inside the input range to corresponded approximation in the output range. It also supports few types of Extrapolation to enable mapping outside the range.

Usage

final double scale = interpolate(
  value: _scrollController.offset,
  inputRange: [
     itemWidth * (index - 2),
     itemWidth * (index - 1),
     itemWidth * index,
     itemWidth * (index + 1),
     itemWidth * (index + 2),
  ],
  outputRange: [0.8, 0.8, 1.0, 0.8, 0.8],
  extrapolate: Extrapolate.extend,
);

inputRange, outputRange

• The inputRange is the range of the input values.
• The outputRange is the range of the output values.
• The output value is calculated by interpolating between the two values in the input range.
• The inputRange and outputRange must have the same length.

Extrapolate

• The extrapolate argument determines how the input value is extrapolated beyond the input range.
• If extrapolate is Extrapolate.identity, the inputRange values are assumed to be increasing and the output value is clamped to the range.
• If extrapolate is Extrapolate.extend, the inputRange values are assumed to be increasing and the output value is extended beyond the range.
• If extrapolate is Extrapolate.clamp, the inputRange values are assumed to be increasing and the output value is clamped to the range.

Credits

• @Nghi-NV