Angular 16 Multiple Images Upload with Preview example

In this tutorial, I will show you way to build Angular 16 Multiple Image Upload with Preview example to Web API/Rest API using FormData and Bootstrap Progress Bars.

More Practice:
– Angular + Spring Boot: File upload example
– Angular + Node Express: File Upload example
– Angular 16 CRUD example with Rest API
– Angular 16 Form Validation example
– Angular 16 JWT Authentication & Authorization example
– Using Material: Angular Material 16 Image upload with Preview example

Contents

Overview
Technology
Rest API for Multiple Image Upload & Storage
Setup Angular 16 Project
Angular 16 Multiple Image upload with Preview Project
Set up App Module
Add Bootstrap to the project
Create Angular Service for Upload Files
Create Angular 16 Component for Upload Multiple Images
Add Upload Images Component to App Component
Run the App
Further Reading
Conclusion

Overview

We will create an Angular 16 Multiple Image upload with Preview application in that user can:

upload multiple Images
see the preview of images that will be uploaded
see the upload process (percentage) of all uploading images
view all uploaded images
download image by clicking on the file name

Here are screenshots of our Angular App:

– Before upload:

– When Multiple Images Upload is done:

– List of Images Display with download Urls:

– Show status for each image upload:

Technology

Angular 16
RxJS 7
Bootstrap 4

Rest API for Multiple Image Upload & Storage

Here are Rest APIs that we will use Axios to make HTTP requests:

Methods	Urls	Actions
POST	/upload	upload a File
GET	/files	get List of Files (name & url)
GET	/files/[filename]	download a File

You can find how to implement the Rest APIs Server at one of following posts:
– Node.js Express File Upload Rest API example
– Node.js Express File Upload to MongoDB example
– Node.js Express File Upload to Google Cloud Storage example
– Spring Boot Multipart File upload (to static folder) example

Setup Angular 16 Project

Let’s open cmd and use Angular CLI to create a new Angular Project as following command:

ng new angular-16-multiple-image-upload-preview
? Would you like to add Angular routing? No
? Which stylesheet format would you like to use? CSS

We also need to generate some Components and Services:

ng g s services/file-upload
ng g c components/upload-images

Now you can see that our project directory structure looks like this.

Angular 16 Multiple Image upload with Preview Project

Let me explain it briefly.

– We import necessary library, components in app.module.ts.
– file-upload.service provides methods to save File and get Files from Rest Apis Server.
– upload-images.component contains image upload for multiple images form, preview, some progress bars, display list of images.
– app.component is the container that we embed all components.
– index.html/style.css for importing the Bootstrap.

Set up App Module

Open app.module.ts and import HttpClientModule:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HttpClientModule } from '@angular/common/http';

import { AppComponent } from './app.component';
import { UploadImagesComponent } from './components/upload-images/upload-images.component';

@NgModule({
  declarations: [
    AppComponent,
    UploadImagesComponent
  ],
  imports: [
    BrowserModule,
    HttpClientModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Add Bootstrap to the project

Open index.html and add following line into <head> tag:

<!DOCTYPE html>
<html lang="en">
  <head>
    ...
    <link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/css/bootstrap.min.css" />
  </head>
  ...
</html>

Another way is installing Bootstrap module with command: npm install [email protected].
Then add following code into src/style.css:

@import "~bootstrap/dist/css/bootstrap.css";

Create Angular Service for Upload Files

This service will use Angular HttpClient to send HTTP requests.
There are 2 functions:

upload(file): returns Observable<HttpEvent<any>> that we’re gonna use for tracking progress
getFiles(): returns a list of Files’ information as Observable object

services/file-upload.service.ts

import { Injectable } from '@angular/core';
import { HttpClient, HttpRequest, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class FileUploadService {

  private baseUrl = 'http://localhost:8080';

  constructor(private http: HttpClient) { }

  upload(file: File): Observable<HttpEvent<any>> {
    const formData: FormData = new FormData();

    formData.append('file', file);

    const req = new HttpRequest('POST', `${this.baseUrl}/upload`, formData, {
      reportProgress: true,
      responseType: 'json'
    });

    return this.http.request(req);
  }

  getFiles(): Observable<any> {
    return this.http.get(`${this.baseUrl}/files`);
  }
}

– FormData is a data structure that can be used to store key-value pairs. We use it to build an object which corresponds to an HTML form with append() method.

– We set reportProgress: true to exposes progress events. Notice that this progress event are expensive (change detection for each event), so you should only use when you want to monitor it.

– We call the request(PostRequest) & get() method of HttpClient to send an HTTP POST & Get request to the Multiple Files Upload Rest server.

Create Angular 16 Component for Upload Multiple Images

Let’s create a Multiple Images Upload UI with Preview, Progress Bars, Card, Button and Message.

First we need to use the following imports:

upload-images.component.ts

import { Component, OnInit } from '@angular/core';
import { HttpEventType, HttpResponse } from '@angular/common/http';
import { Observable } from 'rxjs';
import { FileUploadService } from 'src/app/services/file-upload.service';

Then we define the some variables and inject FileUploadService as follows:

export class UploadImagesComponent implements OnInit {

  selectedFiles?: FileList;
  progressInfos: any[] = [];
  message: string[] = [];

  previews: string[] = [];
  imageInfos?: Observable<any>;

  constructor(private uploadService: FileUploadService) { }
}

The progressInfos is an array that contains items for display upload progress of each images. Each item will have 2 fields: percentage & fileName.

Next we define selectFiles() method. It helps us to get the selected Images that we’re gonna upload.

selectFiles(event: any): void {
  this.message = [];
  this.progressInfos = [];
  this.selectedFiles = event.target.files;

  this.previews = [];
  if (this.selectedFiles && this.selectedFiles[0]) {
    const numberOfFiles = this.selectedFiles.length;
    for (let i = 0; i < numberOfFiles; i++) {
      const reader = new FileReader();

      reader.onload = (e: any) => {
        console.log(e.target.result);
        this.previews.push(e.target.result);
      };

      reader.readAsDataURL(this.selectedFiles[i]);
    }
  }
}

We use FileReader with readAsDataURL() method to get the image preview URL and put it into previews array. This method produces data as a data: URL representing the file’s data as a base64 encoded string. The URL life is tied to the document in the window on which it was created.

Also use selectedFiles array for accessing current selected Files.

Now we iterate over the selected Files above and call upload() method on each file item.

uploadFiles(): void {
  this.message = [];

  if (this.selectedFiles) {
    for (let i = 0; i < this.selectedFiles.length; i++) {
      this.upload(i, this.selectedFiles[i]);
    }
  }
}

Next we define upload() method for uploading each image:

upload(idx: number, file: File): void {
  this.progressInfos[idx] = { value: 0, fileName: file.name };

  if (file) {
    this.uploadService.upload(file).subscribe({
      next: (event: any) => {
        if (event.type === HttpEventType.UploadProgress) {
          this.progressInfos[idx].value = Math.round(100 * event.loaded / event.total);
        } else if (event instanceof HttpResponse) {
          const msg = 'Uploaded the file successfully: ' + file.name;
          this.message.push(msg);
          this.imageInfos = this.uploadService.getFiles();
        }
      },
      error: (err: any) => {
        this.progressInfos[idx].value = 0;
        const msg = 'Could not upload the file: ' + file.name;
        this.message.push(msg);
      }});
  }
}

We use idx for accessing index of the current File to work with progressInfos array. Then we call uploadService.upload() method on the file.

The progress will be calculated basing on event.loaded and event.total.
If the transmission is done, the event will be a HttpResponse object. At this time, we call uploadService.getFiles() to get the files’ information and assign the result to imageInfos variable.

We also need to do this work in ngOnInit() method:

ngOnInit(): void {
  this.imageInfos = this.uploadService.getFiles();
}

Now we create the HTML template of the Image Upload with Preview UI.
Add the following content to upload-images.component.html file:

<div *ngFor="let progressInfo of progressInfos" class="mb-2">
  <span>{{ progressInfo.fileName }}</span>
  <div class="progress">
    <div
      class="progress-bar progress-bar-info progress-bar-striped"
      role="progressbar"
      attr.aria-valuenow="{{ progressInfo.value }}"
      aria-valuemin="0"
      aria-valuemax="100"
      [ngStyle]="{ width: progressInfo.value + '%' }"
    >
      {{ progressInfo.value }}%
    </div>
  </div>
</div>

<div class="row">
  <div class="col-8">
    <label class="btn btn-default p-0">
      <input type="file" accept="image/*" multiple (change)="selectFiles($event)" />
    </label>
  </div>

  <div class="col-4">
    <button
      class="btn btn-success btn-sm"
      [disabled]="!selectedFiles"
      (click)="uploadFiles()"
    >
      Upload
    </button>
  </div>
</div>

<div>
  <img *ngFor='let preview of previews' [src]="preview" class="preview">
</div>

<div *ngIf="message.length" class="alert alert-secondary my-3" role="alert">
  <ul *ngFor="let msg of message; let i = index">
    <li>{{ msg }}</li>
  </ul>
</div>

<div class="card mt-3">
  <div class="card-header">List of Images</div>
  <ul
    class="list-group list-group-flush"
    *ngFor="let image of imageInfos | async"
  >
    <li class="list-group-item">
      <p><a href="{{ image.url }}">{{ image.name }}</a></p>
      <img src="{{ image.url }}" alt="{{ image.name }}" height="80px" />
    </li>
  </ul>
</div>

upload-images.component.css

.preview {
  max-width: 200px;
}

Add Upload Images Component to App Component

Open app.component.html and embed the Upload Images Component with <app-upload-images> tag.

<div class="container" style="width:650px">
  <div class="my-3">
    <h3>bezkoder.com</h3>
    <h4>{{ title }}</h4>
  </div>

  <app-upload-images></app-upload-images>
</div>

app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'Angular 16 Multiple Image Upload with Preview';
}

Run the App

If you use one of following server:
– Node.js Express File Upload Rest API example
– Node.js Express File Upload to MongoDB example
– Node.js Express File Upload to Google Cloud Storage example
– Spring Boot Multipart File upload (to static folder) example

You need run with port 8081 for CORS origin http://localhost:8081 with command:
ng serve --port 8081

Open Browser with url http://localhost:8081/ and check the result.

Or run on Stackblitz:

Conclusion

Today we’re learned how to build an example for multiple Images upload with preview using Angular 16 and Bootstrap 4. We also provide the ability to show list of images and display multiple progress bars.

The source code for the Angular 16 Client is uploaded to Github.