init

README.md

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+识别 QR码 图片  
+> 整理自 [jsqrcode](https://github.com/LazarSoft/jsqrcode)
+
+**修改点:**  
+1. 模块化
+2. 剥离识别函数,改成适合服务端使用 
+3. 需要用其它方法把图片转为 `ImageData` 提供给解码函数
+
+**demo web**
+```html
+<input id="file" type="file">
+```
+
+js: 
+```js
+var qrcodeDecode = require('qrcode-decode');
+
+document.getElementById('file').onchange = function (event) {
+	var file = event.target.files[0];
+	new Promise(function (ok, no) {
+		var reader = new FileReader();
+		reader.onload = evt => {
+			ok(evt.target.result);
+		};
+		reader.readAsDataURL(file);
+	}).then((src)=>{
+		return new Promise(function(ok){
+			var img = new Image();
+			img.src = src;
+			img.onload = function(){
+				var canvas = document.createElement("canvas");
+				var ctx = canvas.getContext('2d');
+				canvas.width = img.width;
+				canvas.height = img.height;
+				ctx.drawImage(img,0,0,canvas.width,canvas.height)
+				var imageData = ctx.getImageData(0,0,canvas.width,canvas.height)
+				ok(imageData);
+			}
+		})
+	}).then(data => {
+		return qrcodeDecode(data);
+	}).then(alert);
+}
+```