我想在ng2-pdf-viewer中突出显示一个矩形

import { Component, OnInit, AfterViewInit, ViewChild, ElementRef } from '@angular/core';
import * as PDFJSAnnotate from 'pdfjs-annotate';

@Component({
  selector: 'app-pdf-viewer',
  templateUrl: './pdf-viewer.component.html',
  styleUrls: ['./pdf-viewer.component.css']
})
export class PdfViewerComponent implements OnInit, AfterViewInit {
  @ViewChild('pdfViewer') pdfViewer: ElementRef;

  constructor() { }

  ngOnInit() {
  }

  ngAfterViewInit() {
    const viewer = this.pdfViewer.nativeElement;
    const url = 'path/to/your/pdf/file.pdf';

    PDFJSAnnotate.getStoreAdapter().addAnnotation({
      type: 'rect',
      width: 100,
      height: 50,
      x: 100,
      y: 100,
      color: 'blue',
      strokeWidth: 2
    }).then(() => {
      PDFJSAnnotate.render(viewer, url, null);
    });
  }
}