刚刚开始接触canvas，写个验证码小功能练练手，实现效果图如下：
主要代码如下:
html
<!DOCTYPE html>
<html lang=\"en\">
<head>
<meta charset=\"UTF-8\">
<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">
<meta http-equiv=\"X-UA-Compatible\" content=\"ie=edge\">
<title>Document</title>
<link rel=\"stylesheet\" href=\"index.css\" rel=\"external nofollow\" >
</head>
<body>
<div class=\"wrapper\">
<div class=\"inputBox\">
<input type=\"text\" class = \'inputCaptcha\' placeholder = \"请输入验证码\">
<span class=\"captchaIcon\"></span>
</div>
<p class=\"errorText\"></p>
<div class=\"canvasBox\">
<div class=\"imageBox\">
<canvas width =300 height=80 id = \'canvasCaptcha\'></canvas>
<input type=\"button\" class=\'refresh\'>
</div>
</div>
<button class=\"captchaSubmit\">submit</button>
</div>
<script src=\'./jquery.js\'></script>
<script src = \'./index.js\'></script>
</body>
</html>
css
* {
margin: 0;
padding: 0;
}
.wrapper {
width: 345px;
border: 1px solid #ccc;
border-radius: 10px;
padding: 20px 10px;
margin: 30px 30px;
}
.inputBox {
width: 345px;
margin: 0 auto 10px;
position: relative;
}
.inputBox .inputCaptcha {
display: inline-block;
height: 50px;
width: 86%;
text-indent: 1em;
border: 1px solid #ddd;
border-radius: 5px;
}
.inputBox .captchaIcon {
display: none;
position: absolute;
top: 50%;
right: 0px;
margin-top: -16px;
width: 32px;
height: 32px;
background-size: 100% 100%;
}
.errorText {
width: 345px;
margin: 0 auto;
font-size: 12px;
color: red;
display: none;
}
.canvasBox {
width: 345px;
margin: 10px auto;
position: relative;
}
#canvasCaptcha {
border-radius: 10px;
}
.canvasBox .refresh {
width: 34px;
height: 34px;
position: absolute;
right: 0px;
top: 50%;
margin-top: -17px;
border: 0;
border-radius: 6px;
background-image: url(\'./images/update.png\');
background-size: cover;
}
.captchaSubmit {
padding: 10px 20px;
background-color: #62b900;
border: 0;
font-size: 20px;
border-radius: 5px;
color: #fff;
}
js
var arr = [0,1,2,3,4,5,6,7,8,9];
for(var i = 65;i < 122;i++){
if(i>90&&i<97){
continue;
}
arr.push(String.fromCharCode(i));
}
//每个验证码可能出现的字母或数字(区分大小写)
var len = arr.length;
//验证码的长度
var canvasStr,value;
//验证码值
function createCanvas(){
canvasStr = \'\';
value = \'\';
for(var i =0 ;i < 6;i++){
var a = arr[Math.floor(Math.random()*len)];
canvasStr += a+\' \';
value += a;
}
//canvas
var oCanvas = document.getElementById(\'canvasCaptcha\');
var ctx = oCanvas.getContext(\'2d\');
var w = oCanvas.width;
var h = oCanvas.height;
var oImg = new Image();
oImg.src = \'./images/bg.jpg\';
oImg.onload = function(){
var pattern = ctx.createPattern(oImg,\'repeat\');
ctx.fillStyle = pattern;
ctx.fillRect(0,0,w,h);
ctx.fillStyle = \'#ccc\';
ctx.textAlign = \'center\';
ctx.font = \'46px Roboto Slab\';
ctx.setTransform(1,-0.12,0.2,1,0,12);
ctx.fillText(canvasStr,w/2,60);
}
}
createCanvas();
//验证输入的验证码与图中验证码时候相等
function captcha(e){
if(e == value){
return true;
}
else{
return false;
}
}
//点击提交按钮时的结果
function showResult(){
var inputValue = $(\'.inputCaptcha\').val();
if(inputValue == \'\' ||inputValue == null || inputValue == \'undefined\'){
$(\'.errorText\').css({display:\'inline-block\'}).html(\'验证码不能为空,请重新输入!\');
$(\'.captchaIcon\').css({display:\'inline-block\',backgroundImage:\"url(\'./images/false.png\')\"});
}else{
var flag = captcha(inputValue);
if(!flag){
$(\'.errorText\').css({display:\'inline-block\'}).html(\'验证码错误,请重新输入!\');
$(\'.captchaIcon\').css({display:\'inline-block\',backgroundImage:\"url(\'./images/false.png\')\"});
}else{
$(\'.captchaIcon\').css({display:\'inline-block\',backgroundImage:\"url(\'./images/true.png\')\"});
}
}
}
$(\'.captchaSubmit\').click(showResult);//提交
$(\'.refresh\').click(createCanvas);//刷新
//点击input框
$(\'.inputCaptcha\').focus(function(){
$(\'.errorText\').add($(\'.captchaIcon\')).fadeOut(100);
})
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。
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