javascript - Interpolation of Colors - Stack Overflow

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I want to interpolate between 2 colors and, given a specific number, generate an array with that number of interpolated colors.

I found that D3 has a method called d3.interpolate(), but I don't know how to use it.

How can I use D3 interpolator to generate an array of colours given the two colors to interpolate and the number of desired interpolated colors?

I want to interpolate between 2 colors and, given a specific number, generate an array with that number of interpolated colors.

I found that D3 has a method called d3.interpolate(), but I don't know how to use it.

How can I use D3 interpolator to generate an array of colours given the two colors to interpolate and the number of desired interpolated colors?

• javascript
• d3.js

Share Improve this question Follow edited Aug 24, 2017 at 13:24 Gerardo Furtado 102k99 gold badges128128 silver badges177177 bronze badges asked Aug 24, 2017 at 9:19 zahmazahma 42244 silver badges1717 bronze badges 1

• 2 You had no question in your post, just a statement, almost a moaning. I edited it to a meaningful question. – Gerardo Furtado Commented Aug 24, 2017 at 13:27

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2 Answers 2

Sorted by: Reset to default 5

For using a D3 interpolator you just need to understand that the argument you'll pass to the interpolator varies from 0 to 1. The API is clear:

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.

So, given this interpolator, going from red to green:

var colorInterpolator = d3.interpolateRgb("red", "green");

We just need to pass the values going from 0 to 1. For example, to create an array with 7 colors, we'll pass these values to the interpolator:

[0, 0.16, 0.33, 0.5, 0.66, 0.83, 1]

Check this demo:

var colorInterpolator = d3.interpolateRgb("red", "green");

var steps = 7;

var colorArray = d3.range(0, (1 + 1 / steps), 1 / (steps - 1)).map(function(d) {
  return colorInterpolator(d)
});

console.log(colorArray)

<script src="https://d3js/d3.v4.min.js"></script>

Now, let's see the colors in that array:

var colorInterpolator = d3.interpolateRgb("red", "green");

var steps = 7;

var colorArray = d3.range(0, (1 + 1 / steps), 1 / (steps - 1)).map(function(d) {
  return colorInterpolator(d)
});

d3.select("body").selectAll(null)
  .data(colorArray)
  .enter()
  .append("div")
  .attr("class", "myDivs")
  .style("background-color", String)

.myDivs {
  width: 40px;
  height: 40px;
  margin-right: 5px;
  display: inline-block;
}

<script src="https://d3js/d3.v4.min.js"></script>

You might want to check d3-color to see how colors are manipulated and interpolated within d3

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