wordpress-theme-aksrt/assets/js/color-extract.js

/**
 * AKSRT Color Extract
 *
 * Extracts dominant colors from images and applies them as dynamic accents.
 * Uses canvas-based color sampling — no external dependencies.
 *
 * Usage:
 *   <img data-aksrt-color-extract data-aksrt-color-target=".card">
 *   <!-- Will set --aksrt-dynamic-color on .card based on image colors -->
 *
 * @package AKSRT
 */

(function () {
  'use strict';

  var canvas = null;
  var ctx = null;

  function getCanvas() {
    if (!canvas) {
      canvas = document.createElement('canvas');
      canvas.width = 40;
      canvas.height = 40;
      ctx = canvas.getContext('2d', { willReadFrequently: true });
    }
    return { canvas: canvas, ctx: ctx };
  }

  function extractColor(img) {
    try {
      var c = getCanvas();
      c.ctx.drawImage(img, 0, 0, 40, 40);
      var data = c.ctx.getImageData(0, 0, 40, 40).data;

      var r = 0, g = 0, b = 0, count = 0;
      var step = 4; // sample every 4th pixel for speed

      for (var i = 0; i < data.length; i += 4 * step) {
        var pr = data[i], pg = data[i + 1], pb = data[i + 2];
        // Skip very dark or very light pixels
        var brightness = (pr + pg + pb) / 3;
        if (brightness < 20 || brightness > 240) continue;
        // Skip near-transparent
        if (data[i + 3] < 128) continue;

        r += pr;
        g += pg;
        b += pb;
        count++;
      }

      if (count === 0) return null;

      r = Math.round(r / count);
      g = Math.round(g / count);
      b = Math.round(b / count);

      return { r: r, g: g, b: b, hex: rgbToHex(r, g, b) };
    } catch (e) {
      // CORS or tainted canvas — silently fail
      return null;
    }
  }

  function rgbToHex(r, g, b) {
    return '#' + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
  }

  function lighten(r, g, b, amount) {
    return rgbToHex(
      Math.min(255, r + amount),
      Math.min(255, g + amount),
      Math.min(255, b + amount)
    );
  }

  function darken(r, g, b, amount) {
    return rgbToHex(
      Math.max(0, r - amount),
      Math.max(0, g - amount),
      Math.max(0, b - amount)
    );
  }

  function applyColor(target, color) {
    if (!target || !color) return;

    var r = color.r, g = color.g, b = color.b;
    target.style.setProperty('--aksrt-dynamic-color', color.hex);
    target.style.setProperty('--aksrt-dynamic-color-rgb', r + ',' + g + ',' + b);
    target.style.setProperty('--aksrt-dynamic-color-light', lighten(r, g, b, 60));
    target.style.setProperty('--aksrt-dynamic-color-dark', darken(r, g, b, 40));

    // Add a subtle tinted background if target doesn't already have one
    if (!target.style.background && !target.style.backgroundColor) {
      target.style.setProperty('--aksrt-dynamic-bg', 'rgba(' + r + ',' + g + ',' + b + ',0.05)');
    }
  }

  function processImage(img) {
    if (img.dataset.aksrtColorDone) return;

    // Need crossOrigin for canvas access
    if (!img.crossOrigin && img.src.indexOf(window.location.origin) !== 0) {
      img.crossOrigin = 'anonymous';
    }

    function extract() {
      var color = extractColor(img);
      if (!color) return;

      img.dataset.aksrtColorDone = '1';

      var targetSelector = img.dataset.aksrtColorTarget;
      var target = targetSelector
        ? img.closest(targetSelector) || document.querySelector(targetSelector)
        : img.parentElement;

      applyColor(target, color);
    }

    if (img.complete && img.naturalWidth > 0) {
      extract();
    } else {
      img.addEventListener('load', extract, { once: true });
    }
  }

  function init() {
    document.querySelectorAll('[data-aksrt-color-extract]').forEach(processImage);
  }

  // Public API
  window.AksrtColorExtract = {
    extract: extractColor,
    apply: applyColor,
    process: processImage,
    init: init
  };

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', init);
  } else {
    init();
  }
  // AJAX 注入新内容后由 auto_fun 重扫（dataset.aksrtColorDone 标记保证幂等）。
  if (window.jQuery) {
    window.jQuery(document).on('auto_fun', init);
  }
})();