Simple copy paste

Question

I'm using AngularJS and I just want to copy an image from whatever (can be snipping tool) and ctrl+v or paste into a canvas so I can upload to the database.

Can anyone explain me how to do this without Jquery? I would like to not lose the aspect ratio if possible

Edit: I just want to have the signature object filled to send to the API. ticket_id is a number and signature is a blob or byte[]

Surely, there's a simpler way. Otherwise, I'm better off using jquery -.-

   this.signature = {
        ticket_id: null,
        signature: null
    };
    
     this.uploadSignature = function() {

        // Fill signature object ???
        
        console.log(this.signature);

        $http.post(baseUrl + "/signature", this.signature).then(
            function(response) {
                // success callback
                console.log("Signature Submitted!");
            },
            function(response) {
                // failure call back
                console.log("Error while submitting the comment");
        });
    }

.signatureCanvas {
    width: 100%;
    background: #ddd;
}

<div class="signature-div text-center">
  <canvas class="signatureCanvas"></canvas>
  <div class="text-right">
    <button uib-tooltip="Upload Signature" class="btn btn-default">Upload <i class="glyphicon glyphicon-cloud-upload"></i></button>
  </div>
</div>