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 + ")";
}

function drawPic(code) {
	var $canvas = document.getElementById("canvas");
	var _str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
	var _picTxt = "";
	var _num = 4;
	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, _height);
		var deg = randomNum(-25, 25);
		var txt = code[i];
		_picTxt += txt;
		ctx.fillStyle = randomColor(10, 100);
		ctx.font = randomNum(16, 30) + "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;
}