js实现前端水印功能

(function(watermark) {
   window.watermarkdivs = [];
   // 加载水印
   var loadMark = function(settings) {
   	var defaultSettings = {
   		watermark_txt: settings.watermark_txt ? settings.watermark_txt : '请输入自定义内容(50字以内)',
   		watermark_x: settings.watermark_x ? settings.watermark_x : 20, //水印起始位置x轴坐标
   		watermark_y: settings.watermark_y ? settings.watermark_y : 20, //水印起始位置Y轴坐标
   		watermark_rows: settings.watermark_rows ? settings.watermark_rows : 0, //水印行数
   		watermark_cols: settings.watermark_cols ? settings.watermark_cols : 0, //水印列数
   		watermark_x_space: settings.watermark_x_space ? settings.watermark_x_space : 50, //水印x轴间隔
   		watermark_y_space: settings.watermark_y_space ? settings.watermark_y_space : 50, //水印y轴间隔
   		watermark_color: settings.watermark_color ? settings.watermark_color : '#000000', //水印字体颜色
   		watermark_alpha: settings.watermark_alpha ? settings.watermark_alpha : 0.05, //水印透明度，要求设置在大于等于0.005
   		watermark_fontsize: settings.watermark_fontsize ? settings.watermark_fontsize : '18px', //水印字体大小
   		watermark_font: settings.watermark_font ? settings.watermark_font : '宋体', //水印字体
   		watermark_width: settings.watermark_width ? settings.watermark_width : 150, //水印宽度
   		watermark_height: settings.watermark_height ? settings.watermark_height : 100, //水印长度
   		watermark_angle: settings.watermark_angle ? settings.watermark_angle : 15, //水印倾斜度数
   		watermark_bg_alpha: settings.watermark_bg_alpha ? settings.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) - parseInt(defaultSettings.watermark_width / 2);
   	//获取页面最大长度
   	// var page_height = Math.max(document.body.scrollHeight,document.body.clientHeight);
   	// 当前获取某个需要水印区域的div的高度waterMarkImgAreaId为div的id
       var page_height = $("#waterMarkImgAreaId").outerHeight() - 10;

   	// 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.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";
   			mask_div.style.wordWrap = "break-word";
   			//设置一张水印相关属性end
   			//附加到文档碎片中
   			otdiv.appendChild(mask_div);
               //控制页面大小变化时水印字体
   			window.watermarkdivs.push(otdiv); 
   		};
   	};
   	//一次性添加到document中
   	document.body.appendChild(oTemp);
   };
   // 水印加载事件
   watermark.load = function(settings) {
   	loadMark(settings);
       // 监听load事件load 仅用于检测一个完全加载的页面，页面的html、css、js、图片等资源都已经加载完之后才会触发 load 事件
   	// window.addEventListener('load', function() {
   	//	loadMark(settings)
   	//})
       // 当初始的 HTML 文档被完全加载和解析完成之后，DOMContentLoaded 事件被触发，而无需等待样式表、图像和子框架的完成加载
   	//window.addEventListener('DOMContentLoaded', function() {
   	//	loadMark(settings)
   	//})
   };
   // 水印移除事件
   watermark.remove = function() {
   	removeMark();
   }
   // 移除水印
   var removeMark = function() {
   	if (window.watermarkdivs && window.watermarkdivs.length > 0) {
   		document.body.removeChild(document.getElementById('otdivid'))
   		window.watermarkdivs = []
   	}
   }
})(window.watermark = {});