1.基本原理
页面加载后，通过javascript创建页面元素div，并在div元素中创建文本节点，展示水印内容
设置div元素样式，将其zIndex设置一个较高的值，并设置透明度，实现浮在页面的水印效果
核心逻辑如下
var mask_div = document.createElement('div');
mask_div.id = 'mask_div1';
mask_div.appendChild(document.createTextNode("test"));
mask_div.style.position = "absolute";
mask_div.style.left = '20px';
mask_div.style.top = '20px';
mask_div.style.overflow = "hidden";
mask_div.style.zIndex = "9999";
mask_div.style.opacity = 0.3;
document.body.appendChild(mask_div);
2.继续完善
上述示例只在页面某处展示了一个水印，实际应用中往往需要在页面中铺满水印
在满足这种需求同时，下述代码将各种属性以配置方式提供给使用者，可根据需要灵活调用
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:20,//水印行数
watermark_cols:20,//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:0.3,//水印透明度
watermark_fontsize:'18px',//水印字体大小
watermark_font:'微软雅黑',//水印字体
watermark_width:120,//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);
//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";
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";
oTemp.appendChild(mask_div);
};
};
document.body.appendChild(oTemp);
}
3.调用方式
watermark({ watermark_txt: "测试水印" })//传入动态水印内容
//onload时触发水印绘制
window.onload=function(){
watermark({ watermark_txt: "测试水印" });
};
//onresize时触发水印绘制
window.onresize = function () {
watermark({ watermark_txt: "测试水印",watermark_width:50 })
};
