我希望能够在上传文件(图像)之前预览它。预览操作应该在浏览器中全部执行,而不使用Ajax上传图像。

我该怎么做?


当前回答

我已经制作了一个插件,由于互联网,它可以在IE 7+中生成预览效果,但几乎没有限制。我把它放进github页面,这样更容易获取

$(函数(){$(“input[name=file1]”).previewimage({div:“.preview”,imgwidth:180,高度:120});$(“input[name=file2]”).previewimage({div:“.preview 2”,imgwidth:90,高度:90});});.preview>div{显示:内联块;文本对齐:居中;}.preview2>div{显示:内联块;文本对齐:居中;}<script src=“https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js“></script><script src=“https://rawgit.com/andrewng330/PreviewImage/master/preview.image.min.js“></script>预览<div class=“preview”></div>预览2<div class=“preview2”></div><form action=“#”method=“POST”enctype=“multipart/form data”><input-type=“file”name=“file1”><input-type=“file”name=“file2”><input-type=“submit”></form>

其他回答

如果您使用React,这里有一个解决方案:

import * as React from 'react'
import { useDropzone } from 'react-dropzone'

function imageDropper() {
  const [imageUrl, setImageUrl] = React.useState()
  const [imageFile, setImageFile] = React.useState()

  const onDrop = React.useCallback(
    acceptedFiles => {
      const file = acceptedFiles[0]
      setImageFile(file)

      // convert file to data: url
      const reader = new FileReader()
      reader.addEventListener('load', () => setImageUrl(String(reader.result)), false)
      reader.readAsDataURL(file)
    },
    [setImageFile, setImageUrl]
  )
  const { getRootProps, getInputProps, isDragActive } = useDropzone({ onDrop })

  return (
    <div>
      <div {...getRootProps()}>
        {imageFile ? imageFile.name : ''}
        {isDragActive ? <p>Drop files here...</p> : <p>Select image file...</p>}
        <input {...getInputProps()} />
      </div>
      {imageUrl && (
        <div>
          Your image: <img src={imageUrl} />
        </div>
      )}
    </div>
  )
}

这里有一种在上传前使用纯javascript预览图像的简单方法;

//profile_change is the id of the input field where we choose an image
document.getElementById("profile_change").addEventListener("change", function() {

//Here we select the first file among the selected files.
const file = this.files[0];

/*here i used a label for the input field which is an image and this image will 
  represent the photo selected and profile_label is the id of this label */
const profile_label = document.getElementById("profile_label");

//Here we check if a file is selected
if(file) {
    //Here we bring in the FileReader which reads the file info. 
    const reader = new FileReader();
    
    /*After reader loads we change the src attribute of the label to the url of the 
    new image selected*/
    reader.addEventListener("load", function() {
        dp_label.setAttribute("src", this.result);
    })

    /*Here we are reading the file as a url i.e, we try to get the location of the 
    file to set that as the src of the label which we did above*/
    reader.readAsDataURL(file);

}else {
    //Here we simply set the src as default, whatever you want if no file is selected.
    dp_label.setAttribute("src", "as_you_want")
}
});

这里是HTML;

<label for="profile_change">
            <img title="Change Profile Photo" id="profile_label" 
             src="as_you_want" alt="DP" style="height: 150px; width: 150px; 
               border-radius: 50%;" >
</label>
<input style="display: none;" id="profile_change" name="DP" type="file" class="detail form-control">

干净简单J小提琴

当您希望通过div或按钮间接触发事件时,这将非常有用。

<img id="image-preview"  style="height:100px; width:100px;"  src="" >

<input style="display:none" id="input-image-hidden" onchange="document.getElementById('image-preview').src = window.URL.createObjectURL(this.files[0])" type="file" accept="image/jpeg, image/png">

<button  onclick="HandleBrowseClick('input-image-hidden');" >UPLOAD IMAGE</button>


<script type="text/javascript">
function HandleBrowseClick(hidden_input_image)
{
    var fileinputElement = document.getElementById(hidden_input_image);
    fileinputElement.click();
}     
</script>

短双衬套

这是cmlevy答案的大小改进-尝试

<input-type=file oninput=“pic.src=window.URL.createObjectURL(this.files[0])”><img id=“pic”/>

单层解决方案:

下面的代码使用对象URL,在查看大型图像时,它比数据URL更有效(数据URL是包含所有文件数据的巨大字符串,而对象URL只是引用内存中文件数据的短字符串):

<img id=“blah”alt=“your image”width=“100”height=“100”/><输入类型=“文件”onchange=“document.getElementById('blah').src=window.URL.createObjectURL(this.files[0])”>

生成的URL如下:

blob:http%3A//localhost/7514bc74-65d4-4cf0-a0df-3de016824345