js实现图片、文字水印效果

1、代码插件

(function(watermark) {
  window.watermarkdivs = [];
  // 加载水印
  var loadMark = function(settings) {
    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: 0, //水印行数
        watermark_cols: 0, //水印列数
        watermark_x_space: 100, //水印x轴间隔
        watermark_y_space: 50, //水印y轴间隔
        watermark_color: '#000000', //水印字体颜色
        watermark_alpha: 0.5, //水印透明度，要求设置在大于等于0.005
        watermark_fontsize: '18px', //水印字体大小
        watermark_font: '微软雅黑', //水印字体
        watermark_width: 150, //水印宽度
        watermark_height: 100, //水印长度
        watermark_angle: 15, //水印倾斜度数
        watermark_bg_alpha: 0.5 //加透明度导致隐形水印无法读取
    };
    //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];
        }
    }
    
    if (window.watermarkdivs && window.watermarkdivs.length > 0) {
        document.body.removeChild(document.getElementById("otdivid"));
        window.watermarkdivs = [];
    }
    
    //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);
    
    // 创建文档碎片
    var oTemp = document.createDocumentFragment();
    //创建水印外壳div
    var otdiv = document.getElementById("otdivid");
    if (!otdiv) {
      otdiv = document.createElement('div');
      otdiv.id = "otdivid";
      otdiv.style.pointerEvents = "none";
      document.body.appendChild(otdiv);
    }
    
    //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');
        var oText = document.createTextNode(defaultSettings.watermark_txt);
        mask_div.appendChild(oText);
        // 设置一张水印相关属性start
        mask_div.id = 'mask_div' + i + j;
        //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.border="solid #eee 1px";
        mask_div.style.opacity = defaultSettings.watermark_alpha;
        mask_div.style.fontSize = defaultSettings.watermark_fontsize;
        mask_div.style.fontFamily = defaultSettings.watermark_font;
        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";
        //设置一张水印相关属性end
        //附加到文档碎片中
        otdiv.appendChild(mask_div);
        
        window.watermarkdivs.push(otdiv); //控制页面大小变化时水印字体
      };
    };
    //一次性添加到document中
    document.body.appendChild(oTemp);
  };
  
  watermark.load = function(settings) {
    window.onload = function() {
      loadMark(settings);
    };
    window.onresize = function() {
      loadMark(settings);
    };
  };
  
})(window.watermark = {});

2、代码引入

watermark.load({ watermark_txt: "我是水印，我来自https://lmcjl.com/" });

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