p3.component.html

<p style="color:green">題三</p>

<p>
  WidthLength : <input type="number" min="1" step="5"
                [(ngModel)]="widthLength" (change)="showPic()" ><br>
  HeightLength : <input type="number" min="1" step="5"
                [(ngModel)]="heightLength" (change)="showPic()"><br>

  <img [src]='imageUrl '/>
</p>

<router-outlet></router-outlet>