Color-scales NPM

color-scales

A utility mimicking Microsoft Excel's Color Scales conditional formatting, which returns the color of a value in a linear gradient between two color endpoints with defined min and max values.

Basic CodePen Demo

Usage

Install from NPM

npm i color-scales

Import it in your project:

const ColorScale = require("color-scales")

Alternatively, import directly from Skypack, a free CDN for Javascript/TypeScript packages:

import ColorScale from "https://cdn.skypack.dev/color-scales";

Important Classes

ColorScale Class

The ColorScale has the following properties:

min (number): The minimum value of the range.
max (number): The maximum value of the range.
colorStops (string[]): An array of colors that act as color stops for the gradient. The colors are spaced out evenly. At least two colors must be passed in. Example: '#ff0000', '#00ff00', '#0000ff'
alpha (number): The alpha value that indicates the level of transparency/opagueness. E.g. Alpha of 0.8 means 20% transparent. Optional, defaults to 1.

Its constructor is ColorScale(min, max, colorStops, alpha);

The ColorScale class has the following functions:

getColor: Param: number. Returns an instance Color corresponding to the numerical value supplied, calculated based on the class properties above.

Color Class

The Color class is an unexported class. It has the following properties:

r: An integer representing the intensity of the red hue. Ranges from 0 to 255.
g: An integer representing the intensity of the green hue. Ranges from 0 to 255.
b: An integer representing the intensity of the blue hue. Ranges from 0 to 255.
a: The alpha value that indicates the level of transparency/opagueness. E.g. Alpha of 0.8 means 20% transparent. Defaults to 1.

The Color class has the following functions:

toHexString: Returns the equivalent hex string representation. The string will be in lower case. Does not support transparency. Example: "#7f7f7f"
toRGBString: Returns the equivalent RGB string representation. The string will be in lower case. Does not support transparency. Example: "rgb(127,127,127)"
toRGBAString: Returns the equivalent RGBA string representation. The string will be in lower case. Example: "rgba(127,127,127, 0.8)"

Example Usage

Constructor

The following import and constructor creates a ColorScale object.

const ColorScale = require("color-scales");
// Alternatively, import from Skypack, a free CDN for Javascript/TypeScript packages:
// import ColorScale from "https://cdn.skypack.dev/color-scales";

let colorScale = new ColorScale(min, max, colorStops, alpha); // alpha is optional. defaults to 1

where min, max, colorStops, and alpha are replaced by their intended value;

Example:

const ColorScale = require("color-scales");

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"], 0.5); // white to black from 0 to 100 with 50% transparency

Get Color Object

Example:

const ColorScale = require("color-scales");

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"], 0.5); // red to green from 0 to 100
let colorObj = colorScale.getColor(50); // returns new Color(127, 127, 127, 0.5)

Get Hex String

Example 1 (full opacity):

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"]); // passing in no alpha value defaults it to 1
let hexStr = colorScale.getColor(50).toHexString(); // returns "#7f7f7f"

Example 2 (0.5 alpha):

let colorScale = new ColorScale(0, 100,[ "#ffffff", "#000000"], 0.5);
let hexStr = colorScale.getColor(50).toHexString(); // returns "#3f3f3f"

As this will give acolor equivalent to if the transparent color was overlaid on a white background. This package version does not support 8-digit hex values. Thus, if users want to implement true transparency, it is recommended that they use the RGBA string option documented in the next section.

Get RGB String

Example 1 (full opacity):

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"]); // passing in no alpha value defaults it to 1
let rgbStr = colorScale.getColor(50).toRGBString(); returns "rgba(127,127,127)"

Example 2 (0.5 alpha):

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"], 0.5);
let rgbStr = colorScale.getColor(50).toRGBString(); // returns "rgba(63,63,63)"

As this will give color equivalent to if the transparent color was overlaid on a white background. Thus, if users want to implement true transparency, it is recommended that they use the RGBA string option documented in the next section.

Get RGBA String

Example 1 (full opacity):

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"]);
let rgbaStr = colorScale.getColor(50).toRGBAString(); // returns "rgba(127,127,127)"

Example 2 (50% transparent):

let colorScale = new ColorScale(0, 100, ["#ffffff", "#000000"], 0.5);
let rgbaStr = colorScale.getColor(50).toRGBAString(); // returns "rgba(127,127,127, 0.5)"