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我发现了很多关于 html5 图片上传的教程，例如

<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">


  <script type='text/javascript' src='/js/lib/mootools-core-1.4.5-nocompat.js'></script>
  <link rel="stylesheet" type="text/css" href="/css/normalize.css">


  <link rel="stylesheet" type="text/css" href="/css/result-light.css">

  <style type='text/css'>

  </style>



<script type='text/javascript'>//<![CDATA[ 
window.addEvent('load', function() {
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>
  <label>Image File:</label><br/>
<input type="file" id="imageLoader" name="imageLoader"/>
<canvas id="imageCanvas"></canvas>

</body>


</html>

但是如何在不覆盖以前的图像的情况下预览图像。我希望能够上传尽可能多的图像，并根据样式表将它们水平对齐或定位。

4

1 回答 1

1

首先，添加一个占位符，用于保存用户选择的所有图像：

<div id="Placeholder">
    <canvas id="imageCanvas"></canvas>
</div>

现在每次将所选图片添加到占位符所需的JS代码是：

window.onload = function() {
    var counter = 0;
    var imageLoader = document.getElementById('imageLoader');
    var oPlaceholder = document.getElementById('Placeholder');
    imageLoader.addEventListener('change', handleImage, false);
    var originalCanvas = document.getElementById('imageCanvas');
    function handleImage(e){
        counter++;
        var canvas = originalCanvas.cloneNode(true);
        canvas.id += "_" + counter;
        oPlaceholder.appendChild(canvas);
        var ctx = canvas.getContext('2d');
        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]);     
    }
};

现场测试用例。

于 2013-09-02T07:03:51.283 回答