如何在不向服务器发送数据的情况下显示选定的图像? [英] How to display selected image without sending data to server?

问题描述

我正在尝试向客户展示他选择的图像:

I am trying to show the client an image which he has selected:

<input type="file" onchange="showImage(this)"/>

但我无法读取输入的值，因为我检查了 这里.可以显示图片吗?

But I can't read the value of the input, as I checked out here. Is it possible to display the image?

在onchange中，我可以将表单发送到服务器，服务器可以将数据发回，但这真的有必要吗?客户端不能在没有乒乓的情况下向服务器显示数据吗?这是安全问题吗?

In onchange I can send the form to server and server can send the data back, but is it really necessary? Can't the client display the data without the ping-pong to the server? Is it a security issue?

推荐答案

您可以使用 FileReader 用于此的 web-api 对象，请参阅此代码段:

You can use FileReader web-api object for this, see this snippet:

HTML

<input id="src" type="file"/> <!-- input you want to read from (src) -->
<img id="target"/> <!-- image you want to display it (target) -->

javascript

function showImage(src,target) {
  var fr=new FileReader();
  // when image is loaded, set the src of the image where you want to display it
  fr.onload = function(e) { target.src = this.result; };
  src.addEventListener("change",function() {
    // fill fr with image data    
    fr.readAsDataURL(src.files[0]);
  });
}

var src = document.getElementById("src");
var target = document.getElementById("target");
showImage(src,target);

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