用js给网页加上水印背景

	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:100,//水印行数
	        watermark_cols:20,//水印列数
	        watermark_x_space:10,//水印x轴间隔
	        watermark_y_space:10,//水印y轴间隔
	        watermark_color:'#aaa',//水印字体颜色
	        watermark_alpha:0.4,//水印透明度
	        watermark_fontsize:'15px',//水印字体大小
	        watermark_font:'微软雅黑',//水印字体
	        watermark_width:100,//水印宽度
	        watermark_height:80,//水印长度
	        watermark_angle:15//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);
	    var cutWidth = page_width*0.0150;
	    var page_width=page_width-cutWidth;
	    //获取页面最大高度
	    var page_height = Math.max(document.body.scrollHeight,document.body.clientHeight);
	    // var page_height = document.body.scrollHeight+document.body.scrollTop;
	    //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.className = 'mask_div';
		            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";
		            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';//pointer-events:none  让水印不遮挡页面的点击事件
		            //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";
		            //交叉网格显示
		            if((i%2==0)&&(j%2==0)){
		            	oTemp.appendChild(mask_div);
		            }
		            if((i%2==1)&&(j%2==1)){
		            	oTemp.appendChild(mask_div);
		            }
	        };
	    };
	    document.body.appendChild(oTemp);
	}
	watermark({watermark_txt:"此处为水印"});

该代码可复制作为一个独立的js。放到jsp中的body后即可实现。 

结果如图