How can I save canvas as image to Firebase storage?

Question

I'm trying to save canvas as an image to the firebase storage. I have read many articles and questions about saving canvas to server, and tried to implement the same with the below code.

function server(){
    canvas = document.getElementById("c");
    var storageRef = firebase.storage().ref();
    var mountainsRef = storageRef.child('mountains.jpg');
    var image = new Image();
    image.src = canvas.toDataURL("image/png");
    var uploadTask = storageRef.child('images/' + "apple").put(image);
    uploadTask.on('state_changed', function(snapshot){
        // Observe state change events such as progress, pause, and resume
        // See below for more detail
    }, function(error) {
        // Handle unsuccessful uploads
    }, function() {
        // Handle successful uploads on complete
        // For instance, get the download URL: https://firebasestorage.googleapis.com/...
        var downloadURL = uploadTask.snapshot.downloadURL;
    });
}

But when I run the web app, the console shows error:

FirebaseError: Firebase Storage: Invalid argument in put at index 0: Expected Blob or File.

How can I successfully save a canvas to Firebase storage?

score 9 · Accepted Answer · edited May 23 '17 at 12:34

9

Yes this is possible. The problem you are having is that you are trying to upload a dataUrl but firebase's put function only excepts blobs or files. To convert a canvas to a blob use the toBlob function.

canvas.toBlob(function(blob){
  var image = new Image();
  image.src = blob;
  var uploadTask = storageRef.child('images/' + "apple").put(blob);
});

Edit: changed var uploadTask = storageRef.child('images/' + "apple").put(image); to var uploadTask = storageRef.child('images/' + "apple").put(blob);

Also not sure if this will work in your case when i tried it I got a tainted canvas error.

What worked for me was the answer to this question How to convert dataURL to file object in javascript?

edited May 23 '17 at 12:34

Community

1
1

answered Jul 05 '16 at 16:53

alecschrader

371
3
8

i tried your solution but now i'm getting two errors `Firebase Storage: Invalid argument in put at index 0: Expected Blob or File.` and `http://localhost:11080/[object%20Blob] 404 (Not Found)` – pavitran Jul 05 '16 at 17:29
`ERROR DOMException: Failed to execute 'toBlob' on 'HTMLCanvasElement': Tainted canvases may not be exported.` for me – Emeric Apr 29 '19 at 15:30
@Emerica Use image.setAttribute('crossorigin', 'anonymous'); – Don Dilanga May 26 '20 at 20:43
The "image" var is never used..? – John Miller Sep 29 '21 at 19:33

How can I save canvas as image to Firebase storage?

1 Answers1