Can't get height and width of image in javascript

Question

I am trying to retreive the actual height and width of an image through javascript. The image source being used in my case is a BLOB which gets generated as soon as a user inserts a file.

Heres my code:

    var img = document.createElement('img');
    var blob = URL.createObjectURL(e.target.files[0]);
    img.src = blob;
    console.log(img);
    var w = img.width;
    var h = img.height;
    console.log("NEW IMAGE width", w);
    console.log("NEW IMAGE height: ", h);

Here are the logs:

<img src=​"blob:​http%3A/​/​localhost%3A3000/​af3e5a35-8c1c-40b5-ad5a-379c3ab1ec1d">​
NEW IMAGE width 0
NEW IMAGE height:  0

the blob is correct since I can view the image in my browser.

When I create another image in my console with the same blob and try to retreive the height and width everything works just fine.

But when I try to run it like that in my onChange event form the input i just get 0 for height and width.

Answer 1

you should get size after image loaded:

    img.onload = getSize;//measure after loading or you will get 0

Answer 2

How to get height and width of the image in blob objeact? example:

$(function(){
	$("input[name=file_name]").on('change',function(){
		var url = window.URL || window.webkitURL || window.mozURL;
		var src = url.createObjectURL($(this)[0].files[0]);
		$("#box").html('<img src="'+src+'">');
		$("#box img").attr('width','100');
		$('img')[0].onload = function() {
		    console.log($(this).height()); //get image height by jQuery
		    console.log($(this)[0].height)// get image height by javascript
		    console.log($(this)[0].naturalHeight);//get real height by javascript
		    /**
		     * if you want to get the image's width,you can use following code :
		     * $(this).width();
		     * $(this)[0].width;
		     * $(this)[0].naturalWidth;
		     */
		};
	})
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<form method="post" enctype="multipart/form-data">
  <input type="file" name="file_name">
</form>

<div id="box"></div>