nodejs产生图片验证码

原文于
基于html5 canvas

1、ubuntu 下安装
sudo apt-get install libcairo2-dev

sudo npm install canvas

2、nodejs代码

var Canvas = require('./Common/canvas');
var getRandom = function(start,end){
    return start+Math.random()*(end-start);
};
var canvas = new Canvas(50,20);
var ctx = canvas.getContext('2d');
var s  = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
var code = '';
for(var i=0;i<4;i++){
    code+= s.substr(parseInt(Math.random()*36),1);
}
var font= 'bold {FONTSIZE}px Impact';//"Bold Italic {FONTSIZE}px arial,sans-serif";//"13px sans-serif";
var start = 3;
var colors = ["rgb(255,165,0)","rgb(16,78,139)","rgb(0,139,0)","rgb(255,0,0)"];
var trans = {c:[-0.108,0.108],b:[-0.05,0.05]};
var fontsizes = [11,12,13,14,15,16];
for(var i in code){
    ctx.font = font.replace('{FONTSIZE}',fontsizes[Math.round(Math.random()*10)%6]);
    ctx.fillStyle = colors[Math.round(Math.random()*10)%4];//"rgba(0, 0, 200, 0.5)";
    ctx.fillText(code[i], start, 15,50);
    ctx.fillRect();
    //con.translate(start,15);
    //ctx.transform(a,b, c, d, e, f);
    //参考：
    //a:水平缩放，default：1 ,取值：0.89,1.32,-0.56等,
    //b:y轴斜切，default：0 ,取值：-0.89,1.32等,
    //c:x轴斜切，default：0 ,取值：-0.89,1.32等,
    //d:垂直缩放，default：1 ,取值：-0.89，0.88,1.32等,
    //e:平移，default：0 ,取值：-53,52等,
    //f:纵称，default：0 ,取值：-53,52等,
    var c = getRandom(trans['c'][0],trans['c'][1]);
    var b = getRandom(trans['b'][0],trans['b'][1]);
    //alert(c+','+b);
    //ctx.transform(1,b, c, 1, 0, 0);
    start+=11;
}
//参考下面链接；可发送给客户端
console.log('code:'+code);
console.log('+canvas.toDataURL()+'" alt="" />');

//输出文件到out.png.可方便使用
var buf = canvas.toDataURL();
var base64Data = buf.replace(/^data:image\/\w+;base64,/, "");
var dataBuffer = new Buffer(base64Data, 'base64');

var fs = require("fs");
fs.writeFile("out.png", dataBuffer, function(err) {
             if(err){
               console.log("errro！");
             }else{
               console.log("保存成功！");
             }
           });

参考连接：
         
          http://blog.csdn.net/northwind_x/article/details/5874680