OpenHtmlToPdf工具rgba转rgb

使用OpenHtmlToPdf工具将html转pdf时不识别html中的rgba属性，导致颜色显示出现问题

测试字符串

    String pdflFile = "/yourPath/ppm-3.pdf";
    FileOutputStream outputStream = new FileOutputStream(pdflFile);

    try (FileOutputStream fos = new FileOutputStream(pdflFile)) {
      PdfRendererBuilder builder = new PdfRendererBuilder();
      File fontFile = new File(
          "/yourPath/fonts/AlibabaSansSEA-Rg.ttf");

      Font font = Font.createFont(Font.TRUETYPE_FONT, fontFile);
      System.out.println("Font Family: " + font.getFamily());
      builder.useFont(fontFile,
          "Alibaba Sans SEA");
      builder.toStream(fos);
      builder.useFastMode();
      String html = "<meta charset="UTF-8">"
+ "<h1 style ="font-family: 'BabelStoneHan',sans-serif;">中文HTML转PDF示例"
+ "这是一个包含中文的 HTML 内容。"
+ "<table style="width:100%; border-collapse: collapse;font-family: 'BabelStoneHan',sans-serif;">"
+ "<th style="border: 1px solid rgb(10, 18, 10); padding: 8px;font-family: 'BabelStoneHan',sans-serif;">表头1"
+ "<th style="border: 1px solid red; padding: 8px;">表头2"
+ "<th style="border: 1px solid rgba(0, 0, 0, 0.06); padding: 8px;">表头3"
+ "<td style="border: 1px solid black; padding: 8px;">数据1"
+ "<td style="border: 1px solid black; padding: 8px;">数据2"
+ "<td style="border: 1px solid black; padding: 8px;">数据3";
      builder.withHtmlContent(
          html,
          null);
      try {
        builder.run();
      } catch (Exception e) {
        e.printStackTrace();
      }
    } catch (FontFormatException e) {
      e.printStackTrace();
    }

问题官方反馈：https://github.com/danfickle/openhtmltopdf/issues/966

需要将rgba转成rgb格式

自己写了一个转换代码将html中的rgba替换成rgb

  public static final Color BACK_GROUND = new Color(255, 255, 255);
  /**
   * 定义匹配RGBA颜色的正则表达式
   */
  public static final String RGBA_REGEX = "rgba\\s*\\(\\s*(\\d+)\\s*,\\s*(\\d+)\\s*,\\s*(\\d+)\\s*,\\s*([\\d.]+)\\s*\\)";

  /**
   * 编译正则表达式
   */
  public static final Pattern PATTERN = Pattern.compile(RGBA_REGEX);

  public static String rgbaToRgb(String htmlString) {

    Matcher matcher = PATTERN.matcher(htmlString);

    // 替换匹配的RGBA颜色为RGB格式
    StringBuffer sb = new StringBuffer();
    while (matcher.find()) {
      int red = Integer.parseInt(matcher.group(1));
      int green = Integer.parseInt(matcher.group(2));
      int blue = Integer.parseInt(matcher.group(3));
      // alpha
      float alpha = Float.parseFloat(matcher.group(4));
      red = (int) (red * alpha + BACK_GROUND.getRed() * (1 - alpha));
      green = (int) (green * alpha + BACK_GROUND.getGreen() * (1 - alpha));
      blue = (int) (blue * alpha + BACK_GROUND.getBlue() * (1 - alpha));
      // 将RGBA转换为RGB
      String rgbColor = "rgb(" + red + ", " + green + ", " + blue + ")";
      matcher.appendReplacement(sb, rgbColor);
    }
    matcher.appendTail(sb);
    return sb.toString();
  }