In this example, we are going to create an image picker that previews your picture before uploading. The previewer also supports drag and dropping files into the input. In this example, I am only going to cover uploading single files, but you can tinker a bit to get multi file upload working.

image-preview.html

This is the html layout of our image preview

<!-- Icon as placeholder when no file picked -->
<i class="material-icons">cloud_upload</i>

<!-- file input, accepts images only. Detect when file has been picked/changed with Angular's native (change) event listener -->
<input type="file" accept="image/*" (change)="updateSource($event)">

<!-- img placeholder when a file has been picked. shows only when 'source' is not empty -->
<img *ngIf="source" [src]="source" src="">

image-preview.ts

This is the main file for our <image-preview> component

import {
    Component,
    Output,
    EventEmitter,
} from '@angular/core';

@Component({
    selector: 'image-preview',
    styleUrls: [ './image-preview.css' ],
    templateUrl: './image-preview.html'
})
export class MtImagePreviewComponent {

    // Emit an event when a file has been picked. Here we return the file itself
    @Output() onChange: EventEmitter<File> = new EventEmitter<File>();

    constructor() {}

    // If the input has changed(file picked) we project the file into the img previewer
    updateSource($event: Event) {
        // We access he file with $event.target['files'][0]
        this.projectImage($event.target['files'][0]);
    }

    // Uses FileReader to read the file from the input
    source:string = '';
    projectImage(file: File) {
        let reader = new FileReader;
        // TODO: Define type of 'e'
        reader.onload = (e: any) => {
            // Simply set e.target.result as our <img> src in the layout
            this.source = e.target.result;
            this.onChange.emit(file);
        };
        // This will process our file and get it's attributes/data
        reader.readAsDataURL(file);
    }
}

another.component.html

<form (ngSubmit)="submitPhoto()">
    <image-preview (onChange)="getFile($event)"></image-preview>
    <button type="submit">Upload</button>
</form>

And that's it. Way more easier than it was in AngularJS 1.x. I actually made this component based on an older version I made in AngularJS 1.5.5.

Import ReactiveFormsModule, and then

import { Component, OnInit, OnDestroy } from '@angular/core';
import { FormControl } from '@angular/forms';
import { Subscription } from 'rxjs';

@Component({
  selector: 'component',
  template: `
    <input [formControl]="control" />
    <div *ngFor="let item of content">
      {{item.id}} - {{item.name}}
    </div>
  `
})
export class MyComponent implements OnInit, OnDestroy {

  public control = new FormControl('');

  public content: { id: number; name: string; }[];
  
  private originalContent = [
    { id: 1, name: 'abc' },
    { id: 2, name: 'abce' },
    { id: 3, name: 'ced' }
  ];
  
  private subscription: Subscription;
  
  public ngOnInit() {
    this.subscription = this.control.valueChanges.subscribe(value => {
      this.content = this.originalContent.filter(item => item.name.startsWith(value));
    });
  }
  
  public ngOnDestroy() {
    this.subscription.unsubscribe();
  }
  
}