swift-interpolate

This module provides a variety of interpolation methods for blending between two values, replicating d3-interpolate. It is experimental and not recommended to be used in production environments.

To interpolate between 2 numbers:

var i = d3.interpolateNumber(10, 20);
i(0.0); // 10
i(0.2); // 12
i(0.5); // 15
i(1.0); // 20

The returned function i is called an interpolator. Given a starting value a and an ending value b, it takes a parameter t in the domain [0, 1] and returns the corresponding interpolated value between a and b. An interpolator typically returns a value equivalent to a at t = 0 and a value equivalent to b at t = 1.

You can also interpolate between 2 colours:

var c = interpolate(UIColor.whiteColor(), UIColor.orangeColor())
c(0.3) // rgb(1.0, 0.85, 0.7, 1.0)

API Reference

# swift.interpolate(a, b)

Returns an interpolator between the two arbitrary values a and b. The interpolator implementation is based on the type of the end value b, using the following algorithm:

1. If b is a UIColor, interpolateRGB is used.
2. If b is a string, interpolateString is used.
3. If b is an array, interpolateArray is used.
4. Otherwise, interpolateNumber is used.

Based on the chosen interpolator, a is coerced to a suitable corresponding type.

# interpolateNumber(a, b)

Returns an interpolator between the two numbers a and b. The returned interpolator is equivalent to:

function interpolate(t) {
  return a * (1 - t) + b * t;
}

# interpolateArray(a, b)

Returns an interpolator between the two arrays a and b. Internally, an array template is created that is the same length in b. For each element in b, if there exists a corresponding element in a, a generic interpolator is created for the two elements using interpolate. If there is no such element, the static value from b is used in the template. Then, for the given parameter t, the template’s embedded interpolators are evaluated. The updated array template is then returned.

For example, if a is the array [0, 1] and b is the array [1, 10, 100], then the result of the interpolator for t = 0.5 is the array [0.5, 5.5, 100].

# interpolateRGB(a, b)

Returns an RGB color space interpolator between the two colors a and b . The return value of the interpolator is an UIColor instance.