nodejs 基于gm模块生成验证码

var gm = require('gm').subClass({ imageMagick: true })
exports.auto_captcha = function(opt ,cb){
	var a = Math.floor(Math.random()*10);
	var b = Math.floor(Math.random()*10);
	opt.text = a+"+"+b+"=";
	console.log('opt.test is ',opt.text);
	opt.captcha_value =a+b;
	exports.captcha(opt,cb);
}

exports.captcha = function(opt ,cb ){
	var width =opt.width||60;
	var height = opt.height|| 40;
	var font_size = opt.font_size ||20;
	var x = 6;
	var y = (height- font_size)/2+font_size;
	return gm(width,height, opt.bg_color ||"#eeeeee")
	  .setFormat('png')
	  .font(__dirname + "/DejaVuLGCSans.ttf") //解决容器中不能找不到字体的问题。导致图片可以生成，但是图片上面的数字内容显示不出来
	  .fontSize(font_size)
	  .drawLine(parseInt(Math.random()*10+50), parseInt(Math.random()*5), parseInt(Math.random()*60), parseInt(Math.random()*60))
	  .drawLine(parseInt(Math.random()*20)+40, parseInt(Math.random()*10), parseInt(Math.random()*60), parseInt(Math.random()*60))
	  .drawLine(parseInt(Math.random()*30)+30, parseInt(Math.random()*15), parseInt(Math.random()*60), parseInt(Math.random()*60))
	  .drawLine(parseInt(Math.random()*10), parseInt(Math.random()*20), parseInt(Math.random()*60), parseInt(Math.random()*60))
	  .drawLine(parseInt(Math.random()*20), parseInt(Math.random()*25), parseInt(Math.random()*60), parseInt(Math.random()*60))
	  .drawText(x, y, opt.text)
	  .noise("Impulse")
	  .implode(0.3)
	  .stream(function(e,so ,se){
		cb(e, so,se);
	});
}