Get image width and height from the Base64 code in JavaScript

Question

I have a Base64 image encoded that you can find here. How can I get the height and the width of it?

Answer 1

var i = new Image();

i.onload = function(){
  alert(i.width + ", " + i.height);
};

i.src = imageData;

Answer 2

For synchronous use just wrap it into a promise like this:

function getImageDimensions(file) {
  return new Promise (function (resolved, rejected) {
    var i = new Image()
    i.onload = function(){
      resolved({w: i.width, h: i.height})
    };
    i.src = file
  })
}

then you can use await to get the data in synchronous coding style:

var dimensions = await getImageDimensions(file)

Answer 3

I found that using .naturalWidth and .naturalHeight had the best results.

const img = new Image();

img.src = 'https://via.placeholder.com/350x150';

img.onload = function() {
  const imgWidth = img.naturalWidth;
  const imgHeight = img.naturalHeight;

  console.log('imgWidth: ', imgWidth);
  console.log('imgHeight: ', imgHeight);
};

Documentation:

• HTMLImageElement.naturalWidth
• HTMLImageElement.naturalHeight

This is only supported in modern browsers. NaturalWidth and NaturalHeight in IE

Answer 4

A more modern solution is to use HTMLImageElement.decode() instead of the onload event. decode() returns a promise and thus can be used synchronously with await.

Asynchronous use:

let img = new Image();
img.src = "myImage.png";
img.decode().then(() => {
    let width = img.width;
    let height = img.height;
    // Do something with dimensions
});

Synchronous use (inside an async function):

let img = new Image();
img.src = "myImage.png";
await img.decode();
let width = img.width;
let height = img.height;
// Do something with dimensions

Answer 5

Create a hidden <img> with that image and then use jQuery's .width() and . height()

$("body").append("<img id='hiddenImage' src='" + imageData + "' />");
var width = $('#hiddenImage').width();
var height = $('#hiddenImage').height();
$('#hiddenImage').remove();
alert("width:" + width + " height:" + height);

Test here: JSFiddle

The image is not initially created hidden. It gets created, and then you get width and height and then remove it. This may cause a very short visibility in large images. In this case, you have to wrap the image in another container and make that container hidden, not the image itself.

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Another Fiddle that does not add to the DOM as per gp.'s answer: here

Answer 6

const img = new Image();
img.src = dataUrl;
await img.decode();
const width, height =  img.width, img.height;