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How do I resize an image on the client size before upload?

Please follow the below example to Image resizing client-side with JavaScript before upload to the server. In modern browser you can use canvas to load and save images data. All modem browsers are supported to the FileReader.

/// How do I read image using FileReader?
/// Example to read file using FileReader.

<input type='file' accept='image/*' onchange='openFile(event)'><br>
<img id='output'>
<script>
  var openFile = function(event) {
    var input = event.target;

    var reader = new FileReader();
    reader.onload = function(){
      var dataURL = reader.result;
      var output = document.getElementById('output');
      output.src = dataURL;
    };

    reader.readAsDataURL(input.files[0]);
  };
</script>

/// How do I resize an image on the client size before upload?
/// JavaScript compress image before upload.
/// Resize image (client side) on an html form before upload in your applications.

<!doctype html>
<html>
<head>
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />
<title>JavaScript/jQuery - compress image before upload.</title>
<script type="text/javascript">
var fileReader = new FileReader();
var filterType = /^(?:image\/bmp|image\/cis\-cod|image\/gif|image\/ief|image\/jpeg|image\/jpeg|image\/jpeg|image\/pipeg|image\/png|image\/svg\+xml|image\/tiff|image\/x\-cmu\-raster|image\/x\-cmx|image\/x\-icon|image\/x\-portable\-anymap|image\/x\-portable\-bitmap|image\/x\-portable\-graymap|image\/x\-portable\-pixmap|image\/x\-rgb|image\/x\-xbitmap|image\/x\-xpixmap|image\/x\-xwindowdump)$/i;

fileReader.onload = function (event) {
  var image = new Image();
 
  image.onload=function(){
      document.getElementById("original-Img").src=image.src;
      var canvas=document.createElement("canvas");
      var context=canvas.getContext("2d");
      canvas.width=image.width/4;
      canvas.height=image.height/4;
      context.drawImage(image,
          0,
          0,
          image.width,
          image.height,
          0,
          0,
          canvas.width,
          canvas.height
      );
     
      document.getElementById("upload-Preview").src = canvas.toDataURL();
  }
 
  image.src=event.target.result;
};

var loadImageFile = function () {
  var uploadImage = document.getElementById("upload-Image");
 
  //check and retuns the length of uploded file.
  if (uploadImage.files.length === 0) {
    return;
  }
 
  //Is Used for validate a valid file.
  var uploadFile = document.getElementById("upload-Image").files[0];
  if (!filterType.test(uploadFile.type)) {
    alert("Please select a valid image.");
    return;
  }
 
  fileReader.readAsDataURL(uploadFile);
}
</script>
</head>

<body onload="loadImageFile();">
  <form name="uploadForm">
    <table>
      <tbody>
        <tr>
          <td>Select Image - <input id="upload-Image" type="file" onchange="loadImageFile();" /></td>
        </tr>
        <tr>
          <td>Origal Img - <img id="original-Img"/></td>
        </tr>
         <tr>
          <td>Compress Img - <img id="upload-Preview"/></td>
        </tr>
      </tbody>
    </table>
  </form>
</body>
</html>

Result looks like – https://embed.plnkr.co/oyaVFn/

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By Anil Singh | Rating of this article (*****)

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