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?

Answer 1

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?