"poline" is an enigmatic color palette generator, that harnesses the mystical witchcraft of polar coordinates. Its methodology, defying conventional color science, is steeped in the esoteric knowledge of the early 20th century. This magical technology defies explanation, drawing lines between anchors to produce visually striking and otherworldly palettes. It is an indispensable tool for the modern generative sorcerer, and a delight for the eye.

Begin your journey with poline by following this simple incantation:

// Import the magical construct
import { Poline } from 'poline';

// Summon a new palette with default settings (random anchor colors)
const poline = new Poline();

// Behold the colors in HSL format
console.log(poline.colors);

// Or as CSS strings ready for your spells
console.log(poline.colorsCSS);

The use of "Poline" begins with the invocation of its command, which can be performed with or without arguments. If called without, the tool will generate a mesmerizing palette featuring two randomly selected anchors. On the other hand, one can choose to provide their own anchor points, represented as a list of hsl values, for a more personal touch. The power to shape and mold the colors lies in your hands."

new Poline({
  anchorColors: [
    [309, 0.72, 0.80],
    [67, 0.32, 0.08],
    //...
  ],
});

The magic of "Poline" is revealed through its technique of drawing lines between anchor points. The richness of the palette is determined by the number of points, with each connection producing a unique color.

Increasing the number of points will yield an even greater array of colors. By default, four points are used, but this can easily be adjusted through the 'numPoints' property on your Poline instance, as demonstrated in the code example.

new Poline({
  numPoints: 6,
});

The resulting palette is a product of points multiplied by the number of anchor pairs. It can be changed after initialization by setting the numPoints property on your "Poline" instance.

At the heart of "Poline" lies the concept of anchors, the fixed points that serve as the foundation for the creation of color palettes. Anchors are represented as a list of hsl values, which consist of three components: hue [0…360], saturation [0…1], and lightness [0…1].

The choice is yours, whether to provide your own anchor points during initialization or to allow "Poline" to generate a random selection for you by omitting the 'anchorColors' argument. The versatility of Poline extends "Poline" its initial setup, as you can also add anchors to your palette at any time using the 'addAnchorPoint' method. This method accepts either a color as HSL array values or an array of X, Y, Z coordinates, further expanding the possibilities of your color creation.

poline.addAnchorPoint({
  color: [100, 0.91, 0.80]
});

// or

poline.addAnchorPoint({
  xyz: [0.43, 0.89, 0.91]
});

You can also specify where to insert the new anchor by providing an insertAtIndex parameter:

poline.addAnchorPoint({
  color: [200, 0.5, 0.6],
  insertAtIndex: 1 // Insert after the first anchor
});

With this feature, you have the power to fine-tune your palette and make adjustments as your creative vision evolves. So whether you are looking to make subtle changes or bold alterations, "Poline" is always ready to help you achieve your desired result.

The ability to update existing anchors is made possible through the 'updateAnchorPoint' method. This method accepts the reference to the anchor you wish to modify and either a color in the form of HSL representation or an XYZ position array.

poline.updateAnchorPoint({
  point: poline.anchorPoints[0],
  color: [286, 0.22, 0.22]
});

You can also update an anchor by its index:

poline.updateAnchorPoint({
  pointIndex: 1,
  color: [120, 0.8, 0.5]
});

The position function in "Poline" plays a crucial role in determining the distribution of colors between the anchors. It works similar to easing functions and can be imported from the "Poline" module.

A position function is a mathematical function that maps a value between 0 and 1 to another value between 0 and 1. By definition the same position function for all axes "Poline" will draw a straight line between the anchors. The chosen function will determine the distribution of colors between the anchors.

import {
Poline, positionFunctions
} from 'poline';

new Poline({
  positionFunction: 
    positionFunctions.linearPosition,
});

If none is provided, "Poline" will use the default function, which is a sinusoidal function. The following position functions are available and can be included by importing the positionFunctions object from the "Poline" module:

• linearPosition
• exponentialPosition
• quadraticPosition
• cubicPosition
• quarticPosition
• sinusoidalPosition (default)
• asinusoidalPosition
• arcPosition
• smoothStepPosition

Here's a visual representation of how these functions affect the distribution:

By defining different position functions for each axis, you can control the distribution of colors along each axis (positionFunctionX, positionFunctionY, positionFunctionZ). This will draw different arcs and create a diverse range of color palettes.

new Poline({
  positionFunctionX: 
    positionFunctions.sinusoidalPosition,
  positionFunctionY: 
    positionFunctions.quadraticPosition,
  positionFunctionZ: 
    positionFunctions.linearPosition,
});

By default, the palette is not a closed loop. This means that the last color generated is not the same as the first color. If you want the palette to be a closed loop, you can set the closedLoop argument to true.

poline.closedLoop = true;

It is also possible to close the loop after the fact by setting poline.closedLoop = true|false.

With the power of hue shifting, "Poline" provides yet another level of customization. This feature allows you to shift the hue of the colors generated by a certain amount, giving you the ability to animate your palette or create similar color combinations with different hues."

"poline" supports hue shifting. This means that the hue of the colors will be shifted by a certain amount. This can be useful if you want to animate the palette or generate a palette that looks similar to your current palette but using different hues.

poline.shiftHue(1);

The amount is a int or float between -Infinity and Infinity. It will permanently shift the hue of all colors in the palette.

In some situations, you might want to know which anchor is closest to a certain position or color. This method is used in the visualizer to highlight to select the closest anchor on click.

poline.getClosestAnchorPoint(
  {xyz: [x, y, null], maxDistance: .1}
)

The maxDistance argument is optional and will return null if the closest anchor is further away than the maxDistance. Any of the xyz or hsl components can be null. If they are null, they will be ignored.

The 'poline' instance returns all colors as an array of hsl, lch or oklch arrays or alternatively as an array of CSS strings.

poline.colors           // Array of HSL values [[h, s, l], [h, s, l], ...]
poline.colorsCSS        // Array of CSS HSL strings ['hsl(h, s%, l%)', ...]
poline.colorsCSSlch     // Array of CSS LCH strings ['lch(l% c h)', ...]
poline.colorsCSSoklch   // Array of CSS OKLCH strings ['oklch(l% c h)', ...]

To remove an anchor, you can use the removeAnchorPoint method. It either takes an anchor reference or an index as an argument.

poline.removeAnchorPoint({
  point: poline.anchorPoints[
    poline.anchorPoints.length - 1
  ]
});
  // or
poline.removeAnchorPoint({
  index: poline.anchorPoints.length - 1
});

The magical construct of "poline" offers the power to invert the lightness calculation, creating palettes with different visual characteristics. You can toggle this option during initialization or later through the instance property.

// During initialization
const poline = new Poline({
  invertedLightness: true
});

// Or later
poline.invertedLightness = true;

When inverted, colors near the center of the coordinate system will have higher lightness values, while colors at the edge will be darker, creating a different aesthetic in your palette.

To keep the library as lightweight as possible, "poline" only supports the hsl color model out of the box. However, it is easily possible to use other color models by using a library like culori.

import {Poline} from "poline";
import {formatHex} from "culori";
const poline = new Poline(/** options */);

const OKHslColors = [...poline.colors].map(
  c => formatHex({ 
    mode: 'okhsl', 
    h: c[0], 
    s: c[1], 
    l: c[2]
  })
);
const LCHColors = [...poline.colors].map(
  c => formatHex({ 
    mode: 'lch', 
    h: c[0],
    c: c[1] * 51.484,
    l: c[2] * 100,  
  })
);

"poline" can be used to generate CSS gradients with unique color distributions:

const poline = new Poline({
  anchorColors: [
    [210, 0.8, 0.6],  // Blue
    [30, 0.8, 0.6]    // Orange
  ],
  numPoints: 8
});

// Generate a CSS linear gradient
const colors = poline.colorsCSS;
const gradient = `linear-gradient(in oklab, ${colors.join(', ')})`;

// Apply to an element
document.getElementById('gradient').style.background = gradient;

"poline" excels at creating color schemes for data visualization. In this case, this makes a great diverging color scheme for a chart:

// Create a palette with perceptually distinct colors
const poline = new Poline({
  anchorColors: [
    [10, 0.70, 0.90],
    [70, 0.97, 0],
    [260, 0.70, 0.0]
  ],
  positionFunction: positionFunctions.linearPosition,
  numPoints: 7,
  closedLoop: true
});

// Use the colors for chart elements
const chartColors = poline.colorsCSS;

You can animate your "poline" palette to create mesmerizing effects:

const poline = new Poline();
let animationFrame;

function animatePalette() {
  // Shift the hue slightly each frame
  poline.shiftHue(0.5);
  
  // Update elements with new colors
  const elements = document.querySelectorAll('.color-element');
  const colors = poline.colorsCSS;
  
  elements.forEach((el, i) => {
    el.style.backgroundColor = colors[i % colors.length];
  });
  
  animationFrame = requestAnimationFrame(animatePalette);
}

// Start/stop animation
document.getElementById('toggle-animation').addEventListener('click', () => {
  if (animationFrame) {
    cancelAnimationFrame(animationFrame);
    animationFrame = null;
  } else {
    animatePalette();
  }
});

"poline" will conjure mystical errors when improper incantations are attempted. Be prepared to handle these manifestations:

• When providing fewer than two anchor colors: "Must have at least two anchor colors"
• When setting numPoints to less than 1: "Must have at least one point"
• When removing too many anchors: "Must have at least two anchor points"
• When providing invalid parameters: "Point must be initialized with either x,y,z or hsl"
• When the anchor point is not found: "Point not found"

Example of proper error handling:

try {
  const poline = new Poline({
    anchorColors: [[100, 0.5, 0.5]] // Only one anchor color!
  });
} catch (error) {
  console.error('Failed to summon palette:', error.message);
  // Fallback to default settings
  const poline = new Poline();
}

"poline" is written in TypeScript and provides type definitions for all its features. The main types you'll encounter:

// Basic vector types
type Vector2 = [number, number];
type Vector3 = [number, ...Vector2];
type PartialVector3 = [number | null, number | null, number | null];

// Position function type
type PositionFunction = (t: number, reverse?: boolean) => number;

// Options for creating a Poline instance
type PolineOptions = {
  anchorColors: Vector3[];
  numPoints: number;
  positionFunction?: PositionFunction;
  positionFunctionX?: PositionFunction;
  positionFunctionY?: PositionFunction;
  positionFunctionZ?: PositionFunction;
  invertedLightness?: boolean;
  closedLoop?: boolean;
};

// Color point collection
type ColorPointCollection = {
  xyz?: Vector3;
  color?: Vector3;
  invertedLightness?: boolean;
};

"poline" is available as an npm package. Alternatively you can clone it on GitHub.

npm install poline

You can also use the unpkg CDN to include the library in your project. I recommend using the mjs version of the library. This will allow you to use the import syntax. But you can also use the umd version if you prefer to use the script tag.

<script type="module">
  import { 
    Poline 
  } from 'https://unpkg.com/poline?module'
</script>

Behold the arcane interface of "poline", detailed in full for your enlightenment:

constructor(options?: PolineOptions)

• numPoints: number - Get/set the number of points between anchors
• positionFunction: PositionFunction | PositionFunction[] - Get/set the position function(s)
• positionFunctionX: PositionFunction - Get/set the X-axis position function
• positionFunctionY: PositionFunction - Get/set the Y-axis position function
• positionFunctionZ: PositionFunction - Get/set the Z-axis position function
• anchorPoints: ColorPoint[] - Get/set the anchor points
• closedLoop: boolean - Get/set whether the palette forms a closed loop
• invertedLightness: boolean - Get/set whether lightness calculation is inverted
• flattenedPoints: ColorPoint[] - Get all points in a flat array
• colors: Vector3[] - Get all colors as HSL arrays
• colorsCSS: string[] - Get all colors as CSS HSL strings
• colorsCSSlch: string[] - Get all colors as CSS LCH strings
• colorsCSSoklch: string[] - Get all colors as CSS OKLCH strings

• updateAnchorPairs(): void - Update internal anchor pairs
• addAnchorPoint(options: ColorPointCollection & { insertAtIndex?: number }): ColorPoint - Add a new anchor point
• removeAnchorPoint(options: { point?: ColorPoint; index?: number }): void - Remove an anchor point
• updateAnchorPoint(options: { point?: ColorPoint; pointIndex?: number } & ColorPointCollection): ColorPoint - Update an anchor point
• getClosestAnchorPoint(options: { xyz?: PartialVector3; hsl?: PartialVector3; maxDistance?: number }): ColorPoint | null - Find closest anchor point
• shiftHue(hShift?: number): void - Shift the hue of all colors

constructor(options?: ColorPointCollection)

• position: Vector3 - Get/set the XYZ position
• hsl: Vector3 - Get/set the HSL color
• hslCSS: string - Get the CSS HSL string
• oklchCSS: string - Get the CSS OKLCH string
• lchCSS: string - Get the CSS LCH string

• positionOrColor(options: ColorPointCollection): void - Set position or color
• shiftHue(angle: number): void - Shift the hue of the color

All position functions have the signature:

(t: number, reverse?: boolean) => number

Available functions:

• linearPosition
• exponentialPosition
• quadraticPosition
• cubicPosition
• quarticPosition
• sinusoidalPosition
• asinusoidalPosition
• arcPosition
• smoothStepPosition

And thus, the tome of "poline" has been written. Its mystical powers, steeped in the arcane knowledge of the ancients, now reside within these pages. May this compendium serve you in your quest for the ultimate color palette.

The project is MIT licensed and open source. If you find any bugs or have any suggestions please open an issue on GitHub.

Inspired and created with the blessing of Anatoly Zenkov