Question

我想将图像上传到画布，然后使用node webkit运行程序，所以这是我的代码：

<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <title>Slicer</title>
    <script>
        var imageLoader = document.getElementById('imageLoader');
   imageLoader.addEventListener('change', handleImage, false);
   var canvas = document.getElementById('imageCanvas');
  var ctx = canvas.getContext('2d');
function handleImage(e){
var reader = new FileReader();
reader.onload = function(event){
    var img = new Image();
    img.onload = function(){
        canvas.width = img.width;
        canvas.height = img.height;
        ctx.drawImage(img,0,0);
    }
    img.src = event.target.result;
}
reader.readAsDataURL(e.target.files[0]);     
}
    </script>
</head>
<body>
    <h1>Image Slicer</h1>
    <label>Image File:</label><br/>
   <input type="file" id="imageLoader" name="imageLoader"/>
    <canvas id="imageCanvas"></canvas>
</body>
 </html>

但运行节点webkit时出现此错误：

Uncaught node.js Error 

TypeError: Cannot read property 'addEventListener' of null
 at file:///F:/Project/Slicer/html/index.html:8:16

**更新**

我忘了等待加载事件

window.addEventListerner('load', app, false);

将图像上传到Node webkit中的画布

0 个答案: