首先说明：有三个文件：1个H5，一个js（代码较长），一个水印js插件（地址：https://code.jquery.com/jquery-git.js）
所有代码已经上传到github：作者水印github位置
备注：经过测试，该效果在IE7.8.9版本下无法显示水印，其他浏览器版本都可以
网页效果图：
HTML代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type"/>
</head>
<body>
<table border="0" width="800" height="800" align="center" cellpadding="0" cellspacing="0" id="table1" bgcolor="#008b8b">
<tr align="center">
<td>测试页面 测试页面</td>
<td>测试页面 测试页面</td>
</tr>
</table>
</body>
<script src="http://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
<script src="https://code.jquery.com/jquery-git.js"></script>
<script type="text/javascript" src="../js/shuiyin2.js" charset="utf-8"></script>
<script type="text/javascript">
var nowDay = getnowDay();
var nowTime = getnowTime();
$('#table1').watermark({
texts : ["A B C X Y Z +"+nowDay,nowTime], //水印文字
textColor : "#DCDCDC", //文字颜色
textFont : '14px 微软雅黑', //字体
width : 130, //水印文字的水平间距
height : 120, //水印文字的高度间距（低于文字高度会被替代）
textRotate : -20 //-90到0， 负数值，不包含-90
})
</script>
<script>
</script>
</html>水印：shuiyin2.js代码：
(function(){
var watermark = function(self){
this.elem = self;
}
watermark.prototype = {
defaults : {
texts : ['此处水印文字'],
width : 100, //每行水印文字的水平间距
height : 100, //水印文字的高度间距（低于文字高度会被替代）
textRotate : -30 , //文字旋转 度数
textColor : '#ede8e8', //文字颜色
textFont : '15px 微软雅黑' //字体
},
options : {
canvas : []
},
init : function(options){
$.extend(this.options, this.defaults, options);
var $body = $('body'),
can1 = this.__createCanvas($body),
can2 = this.__createCanvas($body),
canAll = this.__createCanvas($body),
settings = this.options,
txtlen = settings.texts.length;
settings.deg = settings.textRotate * Math.PI / 180; //js里的正弦余弦用的是弧度
this.__calcTextSize($body);
var repeatTimes = Math.ceil(screen.width / settings.txts.length / settings.width);
settings.canvasWidth = settings.canvasWidth * repeatTimes;
var extTxts = [];
while(repeatTimes--) extTxts = extTxts.concat(settings.txts);
settings.txts = extTxts;
var fixH = settings.maxWidth * Math.abs(Math.sin(settings.deg)) + Math.cos(settings.deg) * settings.textHeight;
if(fixH > settings.height) settings.height = fixH;
var ctx1 = this.__setCanvasStyle(can1, settings.canvasWidth, settings.height);
var ctx2 = this.__setCanvasStyle(can2, settings.canvasWidth, settings.height);
var ctx = this.__setCanvasStyle(canAll, settings.canvasWidth, settings.height * 2, true);
this.__drawText(ctx1, settings.txts);
this.__drawText(ctx2, settings.txts.reverse());
//合并canvas
ctx.drawImage(can1, 0, 0, settings.canvasWidth, settings.height);
ctx.drawImage(can2, 0, settings.height, settings.canvasWidth, settings.height);
var dataURL = canAll.toDataURL("image/png");
$(this.elem).css('backgroundImage', "url("+ dataURL +")");
//this.__destory();
},
__createCanvas : function($container){
var canvas = document.createElement('canvas');
$container.append(canvas);
this.options.canvas.push(canvas);
return canvas;
},
__calcTextSize : function($container){
var txts = [],
maxWidth = 0,
canvasWidth = 0,
settings = this.options;
$.each(settings.texts, function(i, text){
var span = $('<span style="font:'+settings.textFont+';visibility: hidden;display: inline-block;"> '+text+ '</span>')
.appendTo($container);
var tWidth = span[0].offsetWidth,
tHeight = span[0].offsetHeight;
span.remove();
txts.push({
txt : text,
width : tWidth,
height : tHeight
});
maxWidth = Math.max(maxWidth, tWidth);
settings.textHeight = tHeight;
var shadow = Math.cos(settings.deg) * tWidth;
canvasWidth += (settings.width < shadow ? shadow : settings.width) - tHeight * Math.sin(settings.deg);
});
settings.txts = txts;
settings.maxWidth = maxWidth;
settings.canvasWidth = canvasWidth;
},
__setCanvasStyle : function(canvas, width, height, notextstyle){
canvas.width = width;
canvas.height = height;
canvas.style.display='none';
var ctx = canvas.getContext('2d');
if(!notextstyle){
var deg = this.options.deg,
absSindeg = Math.abs(Math.sin(deg));
ctx.rotate(deg);
//基于视窗的 x、y偏移量
var offset = absSindeg * this.options.height - this.options.textHeight * absSindeg;
var nx = - offset * Math.cos(deg),
ny = - offset * absSindeg;
ctx.translate( nx, ny * absSindeg);
ctx.font = this.options.textFont;
ctx.fillStyle = this.options.textColor;
ctx.textAlign = 'left';
ctx.textBaseline = 'Middle';
}
return ctx;
},
__drawText: function(ctx, txts){
var settings = this.options;
$.each(txts, function(i, obj){
var wnap = (settings.maxWidth - obj.width) / 2 ;
var x = settings.width * Math.cos(settings.deg) * i,
y = - x * Math.tan(settings.deg) + settings.height;
ctx.fillText(obj.txt, x + wnap, y);
});
},
__destory : function(){
$.each(this.options.canvas, function(i, canvas){
canvas.remove();
canvas = null;
});
}
}
$.fn.watermark = function(options){
new watermark(this).init(options);
}
})(jQuery);
function getnowDay() {
var d = new Date();
var year = d.getFullYear();
var month = change(d.getMonth() + 1);
var day = change(d.getDate());
function change(t) {
if (t < 10) {
return "0" + t;
} else {
return t;
}
}
var time = year + '年' + month + '月' + day + '日 ';
return time;
}
function getnowTime() {
var d = new Date();
var hour = change(d.getHours());
var minute = change(d.getMinutes());
var second = change(d.getSeconds());
function change(t) {
if (t < 10) {
return "0" + t;
} else {
return t;
}
}
var time = hour + '时' + minute + '分' + second + '秒';
return time;
}