How to load image from base64 encoded string format http response in nativescript angular

app.component.html

<Image *ngIf="checksign" [src]="sign" class="img-rounded p-l-15 p-r-15 p-t-15" col="0" stretch="aspectFit"></Image>

<Button class="btn btn-primary btn-rounded-sm" col="0" text="Attach" (tap)="onSetsign()"></Button>

Through Html

<Image [src]="'data:image/png;base64,'+auditor.audSignature"
class="img-rounded p-l-15 p-r-15 p-t-15" col="2" stretch="aspectFit"></Image>

app.component.ts

declare var android;
declare var java: any;

public onSetsign() {

//this.ObsArray[0].audSignature - base64 encoded value
let a= android.util.Base64.decode(this.ObsArray[0].audSignature,android.util.Base64.DEFAULT);
let b= new java.lang.String(a);
let c: string = 'data:image/png;base64,' + b;
console.log("check a " + a);
this.sign = a;
this.checksign = true;
}