<form [ngFormModel]="imgUploadFrm"
     (ngSubmit)="onSubmit(imgUploadFrm)">
    <br>
    <div class="input-field">
      <input type="file" id="imgFile" (click)="onChange($event)" >
    </div>
    <button id="btnAdd" type="submit" (click)="showImageBrowseDlg()" )>Add Picture</button>
 </form>

this.renderer.invokeElementMethod(
    this.fileInput.nativeElement, 'dispatchEvent', [event]);

this.fileInput.nativeElement.dispatchEvent(event);

import { Component, Renderer, ElementRef } from '@angular/core';
@Component({
 ...
 template: `
...
<input #fileInput type="file" id="imgFile" (click)="onChange($event)" >
...`
})
class MyComponent {
 @ViewChild('fileInput') fileInput:ElementRef;

 constructor(private renderer:Renderer) {}

 showImageBrowseDlg() {
  // from http://stackoverflow.com/a/32010791/217408
  let event = new MouseEvent('click', {bubbles: true});
  this.renderer.invokeElementMethod(
    this.fileInput.nativeElement, 'dispatchEvent', [event]);
 }
}

this.fileInput.nativeElement.click()