Blob to base64

import { HttpClient } from '@angular/common/http';
import { Observable, Observer } from 'rxjs';
import { switchMap, take } from 'rxjs/operators';

export class BlobToBase64Converter {
  convertBlobToBase64(http: HttpClient, fileUrl: string): Observable<string> {
    return http.get(fileUrl, { responseType: 'blob' }).pipe(
      take(1),
      switchMap((blob: Blob) => this.converter(blob).pipe(take(1)))
    );
  }

  private converter(data: Blob): Observable<string> {
    return Observable.create((observer: Observer<string>) => {
      const reader = new FileReader();
      reader.readAsDataURL(data);
      reader.onloadend = () => {
        observer.next(reader.result as string);
        observer.complete();
      };
      reader.onerror = () => {
        observer.error('Error while converting to base64');
        observer.complete();
      };
    });
  }
}