swOperation/node_modules/@antv/g2/esm/label-transform/contrastReverse.js

import { maxIndex } from 'd3-array';
import { parseToRGB } from '../utils/color';
function getsRGB(s) {
    let c = s / 255;
    c = c <= 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
    return c;
}
function getL(r, g, b) {
    return 0.2126 * getsRGB(r) + 0.7152 * getsRGB(g) + 0.0722 * getsRGB(b);
}
/**
 * Calculate the contrast. see https://webaim.org/resources/contrastchecker/
 * @param foreground
 * @param background
 */
function contrast(foreground, background) {
    const { r, g, b } = foreground;
    const { r: rb, g: gb, b: bb } = background;
    const L1 = getL(r, g, b);
    const L2 = getL(rb, gb, bb);
    return (Math.max(L1, L2) + 0.05) / (Math.min(L1, L2) + 0.05);
}
/**
 * Reverse color for max contrast.
 */
function mostContrast(color, palette) {
    const i = maxIndex(palette, (c) => contrast(color, parseToRGB(c)));
    return palette[i];
}
/**
 * Reverse the label color when the contrast is lower then `threshold`.
 * The default value of `threshold` is 4.5.
 * More about contract, see https://webaim.org/resources/contrastchecker/
 */
export const ContrastReverse = (options) => {
    const { threshold = 4.5, palette = ['#000', '#fff'] } = options;
    return (labels, coordinate) => {
        labels.forEach((l) => {
            const background = l.attr('dependentElement').parsedStyle.fill;
            const foreground = l.parsedStyle.fill;
            const c = contrast(foreground, background);
            if (c < threshold)
                l.attr('fill', mostContrast(background, palette));
        });
        return labels;
    };
};
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