如何通过ng2-file-upload选择图片后立即显示？

import { Component } from '@angular/core';
import { FileUploader } from 'ng2-file-upload';

@Component({
  selector: 'app-upload',
  templateUrl: './upload.component.html',
  styleUrls: ['./upload.component.css']
})
export class UploadComponent {
  public uploader: FileUploader = new FileUploader({ url: 'your-upload-url' });
}

<input type="file" ng2FileSelect [uploader]="uploader" (change)="onFileSelected($event)" />
<img [src]="selectedImage" *ngIf="selectedImage" />

public selectedImage: string;

onFileSelected(event: any): void {
  if (event.target.files && event.target.files.length) {
    const reader = new FileReader();
    reader.onload = (e: any) => {
      this.selectedImage = e.target.result;
    };
    reader.readAsDataURL(event.target.files[0]);
  }
}