【36】一个canvas写的验证码

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<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <canvas id="canvas" width="150" height="50"></canvas>
<script>
    function randomNum(min,max){
        return Math.floor(Math.random()*(max-min)+min);
    }
    function randomColor(min,max){
        var _r = randomNum(min,max);
        var _g = randomNum(min,max);
        var _b = randomNum(min,max);
        return "rgb("+_r+","+_g+","+_b+")";
    }
    document.getElementById("canvas").onclick = function(e){
        e.preventDefault();
        drawPic();
    };
    function drawPic(){
        var $canvas = document.getElementById("canvas");
        var _str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        var _picTxt = "";
        var _num = 6;
        var _width = $canvas.width;
        var _height = $canvas.height;
        var ctx = $canvas.getContext("2d");
        ctx.textBaseline = "bottom";
        ctx.fillStyle = randomColor(180,240);
        ctx.fillRect(0,0,_width,_height);
        for(var i=0; i<_num; i++){
            var x = (_width-10)/_num*i+10;
            var y = randomNum(_height/2,_height);
            var deg = randomNum(-45,45);
            var txt = _str[randomNum(0,_str.length)];
            _picTxt += txt;
            ctx.fillStyle = randomColor(10,100);
            ctx.font = randomNum(16,40)+"px SimHei";
            ctx.translate(x,y);
            ctx.rotate(deg*Math.PI/180);
            ctx.fillText(txt, 0,0);
            ctx.rotate(-deg*Math.PI/180);
            ctx.translate(-x,-y);
        }
        for(var i=0; i<_num; i++){
            ctx.strokeStyle = randomColor(90,180);
            ctx.beginPath();
            ctx.moveTo(randomNum(0,_width), randomNum(0,_height));
            ctx.lineTo(randomNum(0,_width), randomNum(0,_height));
            ctx.stroke();
        }
        for(var i=0; i<_num*10; i++){
            ctx.fillStyle = randomColor(0,255);
            ctx.beginPath();
            ctx.arc(randomNum(0,_width),randomNum(0,_height), 1, 0, 2*Math.PI);
            ctx.fill();
        }
        return _picTxt;
    }
    drawPic();
</script>
</body>
</html>
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【36】一个canvas写的验证码

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