How to convert an image to base64 in JavaScript

Question

I'm trying to write a file upload script for use in a secure corporate intranet and having just a little trouble...

In the following code, I get no errors and all my debugging looks like everything is working, but the end result is always a 'blank' image:

var ctx = document.createElement('canvas');
var img = new Image();
img.onload = function(){
    ctx.drawImage(img,0,0);
}
img.src = $('#UpdateImage:file');

var imgStr = ctx.toDataURL("image/png", "");
document.getElementById("Item_Create_Image_Avatar").src = imgStr;

When I "inspect element" on the 'Item_Create_Image_Avatar' object, the 'src' value looks absolutely perfect:

<img src="data:image/png;base64,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" id="Item_Create_Image_Avatar" style="vertical-align:top">

Why is my image coming in as blank?

I think the problem is with setting the 'src' of the 'img' to a file: img.src = $('#UpdateImage:file'); Then converting that to a 'dataURL' is giving me a base64 string that always shows as blank because it's not using the actual image info... — Nicolai Dutka, Oct 29 '13 at 14:29
possible duplicate of [How to convert image into base64 string using javascript](http://stackoverflow.com/questions/6150289/how-to-convert-image-into-base64-string-using-javascript) — HaNdTriX, Mar 08 '14 at 22:21
Regarding @HaNdTriX link look at his function he wrote, which seems to work great. **[Image to Base64](http://jsfiddle.net/handtrix/YvQ5y/)** — WASasquatch, Apr 21 '14 at 06:20

score 4 · Answer 1 · edited May 23 '17 at 12:17

Found This.

Select a File to Load:
<input id="inputFileToLoad" type="file" onchange="loadImageFileAsURL();" />

<div id="imgTest"></div>


<script type='text/javascript'>

function loadImageFileAsURL(){

    var filesSelected = document.getElementById("inputFileToLoad").files;
    if (filesSelected.length > 0){
        var fileToLoad = filesSelected[0];

        var fileReader = new FileReader();

        fileReader.onload = function(fileLoadedEvent) {
            var srcData = fileLoadedEvent.target.result; // <--- data: base64

            var divTest = document.getElementById("imgTest");
            var newImage = document.createElement('img');
            newImage.src = srcData;

            divTest.innerHTML = newImage.outerHTML;

        }

        fileReader.readAsDataURL(fileToLoad);
    }
}

</script>

EDIT:

Source: How to convert image into base64 string using javascript

Edited a line of your code, since it was having issue with var declaration for document.getElementById("imgTest").innerHTML.. Its now working like a charm... :) — , May 15 '14 at 05:14

devnull69 · Answer 2 · 2014-04-21T06:14:04.650

0

If you want to get the Data URL of the image after it loaded, you should get the Data URL after it loaded

var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var img = new Image();
img.onload = function() {
   ctx.drawImage(img, 0, 0);
   imgStr = canvas.toDataURL("image/png", "");
   document.getElementById("Item_Create_Image_Avatar").src = imgStr;
}
img.src = $('#UpdateImage:file');

EDIT: Included the rest of the code EDIT2: Edited stupid error regarding canvas and its context

edited Apr 21 '14 at 06:14

answered Oct 28 '13 at 20:06

devnull69

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This doesn't work... Now instead of a blank image, I get nothing at all. The image doesn't change in the slightest bit and inspecting the element reveals the 'src' is not getting updated. – Nicolai Dutka Oct 29 '13 at 14:05
I hope you just replace the .onload part of your original code? The rest of your code should remain unchanged. Answer edited accordingly ... – devnull69 Oct 30 '13 at 14:06
document.createElement('canvas') will return canvas, not context – Le Duc Duy Apr 18 '14 at 06:43

How to convert an image to base64 in JavaScript

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