JavaScript实现算数验证码
2019-12-30 本文已影响0人
念念碎平安夜
一、界面
<style type="text/css">
.code_a {
color: #0000ff;
font-size: 12px;
text-decoration: none;
cursor: pointer;
}
#cvs {
cursor: pointer;
}
</style>
<script type="text/javascript" src="js/l32.js" charset="UTF-8"></script>
<script type="text/javascript">
var valicode;
function changeCode(){
var cvs = document.getElementById("cvs");
valicode = drawcode(cvs);
}
function valiCode(){
var code = document.getElementById("inCode").value;
if(code.toString() == valicode.toString()){
return true;
}
else{
document.getElementById("err").innerHTML = "输入的验证码错误！";
changeCode();
return false;
}
}
window.onload = changeCode;
</script>
</head>
<body>
<form action="index.jsp" method="post">
<label>验证码：</label>
<input type="text" id="inCode" name="inCode" />
<canvas id="cvs" onclick="changeCode()"></canvas>
<a class="code_a" onclick="changeCode()">换一张</a><br />
<input type="submit" value="登录" onclick="return valiCode()" />
</form>
<div style="color:red" id="err"></div>
</body>
二、脚本代码绘制图片
//高度、宽度、字符大小、字符集
var w = 80;
var h = 24;
var fontsize = h-6;
var str = "+-*";
//随机生成最大值不超过max的整数
function randInt(max){
return Math.floor(Math.random()*100000%max);
}
//生成随机长度的字符串验证码
function randCode(){
var one = randInt(100);
var two = randInt(100);
var op = str.charAt(randInt(str.length));
return ""+one+op+two+"=";
}
//生成随机颜色
function randColor(){
var r = randInt(256);
var g = randInt(256);
var b = randInt(256);
return "rgb("+r+","+g+","+b+")";
}
//绘制图片
function drawcode(canvas){
var valicode = randCode();
w = 5 + fontsize*valicode.length;
if(canvas != null && canvas.getContext && canvas.getContext("2d")){
//设置显示区域大小
canvas.style.width = w;
//设置画板高宽
canvas.setAttribute("width",w);
canvas.setAttribute("height",h);
//得到画笔
var pen = canvas.getContext("2d");
//绘制背景
pen.fillStyle = "rgb(255,255,255)";
pen.fillRect(0,0,w,h);
//设置水平线位置
pen.textBaseline = "top"; //middle,bottom
//绘制内容
for(var i=0; i<valicode.length; i++){
pen.fillStyle = randColor();
pen.font = "bold "+(fontsize+randInt(3))+"px 微软雅黑";
pen.fillText(valicode.charAt(i), 5+fontsize*i, randInt(5));
}
//绘制噪音线
for(var i=0; i<2; i++){
pen.moveTo(randInt(w)/2, randInt(h)); //设置起点
pen.lineTo(randInt(w), randInt(h)); //设置终点
pen.strokeStyle = randColor();
pen.lineWidth = 2; //线条粗细
pen.stroke();
}
valicode = valicode.substr(0, valicode.length-1);
//eval函数：把字符串当表达式处理
return eval(valicode);
}
}
