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mix.js
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mix.js
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// @flow
import rgba from './rgba'
import parseToRgb from './parseToRgb'
import curry from '../internalHelpers/_curry'
/**
* Mixes two colors together by calculating the average of each of the RGB components.
*
* By default the weight is 0.5 meaning that half of the first color and half the second
* color should be used. Optionally the weight can be modified by providing a number
* as the first argument. 0.25 means that a quarter of the first color and three quarters
* of the second color should be used.
*
* @example
* // Styles as object usage
* const styles = {
* background: mix(0.5, '#f00', '#00f')
* background: mix(0.25, '#f00', '#00f')
* background: mix(0.5, 'rgba(255, 0, 0, 0.5)', '#00f')
* }
*
* // styled-components usage
* const div = styled.div`
* background: ${mix(0.5, '#f00', '#00f')};
* background: ${mix(0.25, '#f00', '#00f')};
* background: ${mix(0.5, 'rgba(255, 0, 0, 0.5)', '#00f')};
* `
*
* // CSS in JS Output
*
* element {
* background: "#7f007f";
* background: "#3f00bf";
* background: "rgba(63, 0, 191, 0.75)";
* }
*/
function mix(weight: number = 0.5, color: string, otherColor: string): string {
const parsedColor1 = parseToRgb(color)
const color1 = {
...parsedColor1,
alpha: typeof parsedColor1.alpha === 'number' ? parsedColor1.alpha : 1,
}
const parsedColor2 = parseToRgb(otherColor)
const color2 = {
...parsedColor2,
alpha: typeof parsedColor2.alpha === 'number' ? parsedColor2.alpha : 1,
}
// The formular is copied from the original Sass implementation:
// http://sass-lang.com/documentation/Sass/Script/Functions.html#mix-instance_method
const alphaDelta = color1.alpha - color2.alpha
const x = (weight * 2) - 1
const y = x * alphaDelta === -1 ? x : (x + alphaDelta)
const z = (1 + (x * alphaDelta))
const weight1 = ((y / z) + 1) / 2.0
const weight2 = 1 - weight1
const mixedColor = {
red: Math.floor((color1.red * weight1) + (color2.red * weight2)),
green: Math.floor((color1.green * weight1) + (color2.green * weight2)),
blue: Math.floor((color1.blue * weight1) + (color2.blue * weight2)),
alpha: color1.alpha + ((color2.alpha - color1.alpha) * (weight / 1.0)),
}
return rgba(mixedColor)
}
export default curry(mix)