网页盲水印实现

由此文章：阿里月饼事件还没完 泄露内网截图的员工可能也要走了

有人问到如何做到能找到截图员工

此技术为盲水印

先贴代码：

function watermark(settings) {

  //默认设置
  var defaultSettings={
    watermark_txt:"text",
    watermark_x:20,//水印起始位置x轴坐标
    watermark_y:20,//水印起始位置Y轴坐标
    watermark_rows:5,//水印行数
    watermark_cols:5,//水印列数
    watermark_x_space:10,//水印x轴间隔
    watermark_y_space:90,//水印y轴间隔
    watermark_color:'#000000',//水印字体颜色
    watermark_alpha:0.005,//水印透明度
    watermark_fontsize:'80px',//水印字体大小
    watermark_font:'微软雅黑',//水印字体
    watermark_width:500,//水印宽度
    watermark_height:90,//水印长度
    watermark_angle:25//水印倾斜度数
  };
  //采用配置项替换默认值，作用类似jquery.extend
  if(arguments.length===1&&typeof arguments[0] ==="object" )
  {
    var src=arguments[0]||{};
    for(key in src)
    {
      if(src[key]&&defaultSettings[key]&&src[key]===defaultSettings[key])
        continue;
      else if(src[key])
        defaultSettings[key]=src[key];
    }
  }

  var oTemp = document.createDocumentFragment();

  //获取页面最大宽度
  var page_width = Math.max(document.body.scrollWidth,document.body.clientWidth);
  //获取页面最大长度
  var page_height = Math.max(document.body.scrollHeight,document.body.clientHeight);

  //如果将水印列数设置为0，或水印列数设置过大，超过页面最大宽度，则重新计算水印列数和水印x轴间隔
  if (defaultSettings.watermark_cols == 0 || (parseInt(defaultSettings.watermark_x + defaultSettings.watermark_width *defaultSettings.watermark_cols + defaultSettings.watermark_x_space * (defaultSettings.watermark_cols - 1)) > page_width)) {
    defaultSettings.watermark_cols = parseInt((page_width-defaultSettings.watermark_x+defaultSettings.watermark_x_space) / (defaultSettings.watermark_width + defaultSettings.watermark_x_space));
    defaultSettings.watermark_x_space = parseInt((page_width - defaultSettings.watermark_x - defaultSettings.watermark_width * defaultSettings.watermark_cols) / (defaultSettings.watermark_cols - 1));
  }
  //如果将水印行数设置为0，或水印行数设置过大，超过页面最大长度，则重新计算水印行数和水印y轴间隔
  if (defaultSettings.watermark_rows == 0 || (parseInt(defaultSettings.watermark_y + defaultSettings.watermark_height * defaultSettings.watermark_rows + defaultSettings.watermark_y_space * (defaultSettings.watermark_rows - 1)) > page_height)) {
    defaultSettings.watermark_rows = parseInt((defaultSettings.watermark_y_space + page_height - defaultSettings.watermark_y) / (defaultSettings.watermark_height + defaultSettings.watermark_y_space));
    defaultSettings.watermark_y_space = parseInt(((page_height - defaultSettings.watermark_y) - defaultSettings.watermark_height * defaultSettings.watermark_rows) / (defaultSettings.watermark_rows - 1));
  }
  var x;
  var y;
  for (var i = 0; i < defaultSettings.watermark_rows; i++) {
    y = defaultSettings.watermark_y + (defaultSettings.watermark_y_space + defaultSettings.watermark_height) * i;
    for (var j = 0; j < defaultSettings.watermark_cols; j++) {
      x = defaultSettings.watermark_x + (defaultSettings.watermark_width + defaultSettings.watermark_x_space) * j;

      var mask_div = document.createElement('div');
      mask_div.id = 'mask_div' + i + j;
      mask_div.appendChild(document.createTextNode(defaultSettings.watermark_txt));
      //设置水印div倾斜显示
      mask_div.style.webkitTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
      mask_div.style.MozTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
      mask_div.style.msTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
      mask_div.style.OTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
      mask_div.style.transform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
      mask_div.style.visibility = "";
      mask_div.style.position = "absolute";
      //选不中
      mask_div.style.left = x + 'px';
      mask_div.style.top = y + 'px';
      mask_div.style.overflow = "hidden";
      mask_div.style.zIndex = "9999";
      mask_div.style.pointerEvents = "none";
      //mask_div.style.border="solid #eee 1px";
      mask_div.style.opacity = defaultSettings.watermark_alpha;
      mask_div.style.fontSize = defaultSettings.watermark_fontsize;
      mask_div.style.color = defaultSettings.watermark_color;
      mask_div.style.textAlign = "center";
      mask_div.style.width = defaultSettings.watermark_width + 'px';
      mask_div.style.height = defaultSettings.watermark_height + 'px';
      mask_div.style.display = "block";
      oTemp.appendChild(mask_div);
    };
  };
  document.body.appendChild(oTemp);
}
watermark({ watermark_txt:'xhily'})

代码作用是增加一个透明度只有0.005的很多水印

开始实验：

打开百度

F12，选择console 将上述代码粘贴并回车

然后尝试截图

打开PS，并将截图拖入PS

添加一个纯黑图层，将叠加方式改为 颜色加深

水印就显示出来了