fast-average-color/src/algorithm/simple.js

A simple library that calculates the average color of images, videos and canvas in browser environment.

import { isIgnoredColor } from './ignoredColor';

export default function simpleAlgorithm(arr, len, options) {
    let redTotal = 0;
    let greenTotal = 0;
    let blueTotal = 0;
    let alphaTotal = 0;
    let count = 0;

    const ignoredColor = options.ignoredColor;

    for (let i = 0; i < len; i += options.step) {
        const alpha = arr[i + 3];
        const red = arr[i] * alpha;
        const green = arr[i + 1] * alpha;
        const blue = arr[i + 2] * alpha;

        if (ignoredColor && isIgnoredColor(arr, i, ignoredColor)) {
            continue;
        }

        redTotal += red;
        greenTotal += green;
        blueTotal += blue;
        alphaTotal += alpha;
        count++;
    }

    return alphaTotal ? [
        Math.round(redTotal / alphaTotal),
        Math.round(greenTotal / alphaTotal),
        Math.round(blueTotal / alphaTotal),
        Math.round(alphaTotal / count)
    ] : options.defaultColor;
}