将 JS 代码放入图片文件

	var code = 'alert("hello image.");';
	var w=6,h=8; // 宽和高的计算方法 w * h * 32 / 8 = code.length
	
	// 按3个字符的长度分段
	var codeArray = code.match(/.{3}/g);
	if(codeArray.length * 3 < code.length){
		codeArray.push( code.substring( codeArray.length * 3 - 1) );
	}
	for(var i = 0, cl = codeArray.length; i < cl; c++){
		codeArray[i] = codeArray[i]+String.fromCharCode(255);
	}
	code = codeArray.join('');

	// 将代码转为ASCII
	var buffer = [];
	for(var i = 0, l = code.length; i < l; i++){
		buffer.push(code.charCodeAt(i));
	}
	buffer = new Uint8ClampedArray(buffer);

	// 将代码转换为图片数据
	var imageData= new ImageData(w, h);
	imageData.data.set(buffer);
	var canvas = document.createElement('canvas');
	canvas.width = w;
	canvas.height = h;
	var context = canvas.getContext("2d");
	context.putImageData(imageData,0,0);
	base64img = canvas.toDataURL('image/png');
	
	// 在页面中插入图片
	var img=document.createElement("img");
	img.src=base64img;
	console.log(base64img);
	document.body.appendChild(img);

从图片文件中取出 JS 代码