Optimizing images

Images are a big part of many applications, and can be a major contributor to application performance problems, including low Core Web Vitals scores.

Image optimization can be a complex topic, but Angular handles most of it for you, with the NgOptimizedImage directive. In this activity, you'll learn how to use NgOptimizedImage to ensure your images are loaded efficiently.

Import the NgOptimizedImage directive

In order to leverage the NgOptimizedImage directive, first import it from the @angular/common library and add it to the component imports array.

      import { NgOptimizedImage } from '@angular/common';@Component({  imports: [NgOptimizedImage],  ...})

Update the src attribute to be ngSrc

To enable the NgOptimizedImage directive, swap out the src attribute for ngSrc. This applies for both static image sources (i.e., src) and dynamic image sources (i.e., [src]).

      import { NgOptimizedImage } from '@angular/common';@Component({  template: `    ...    <li>      Static Image:      <img ngSrc="/assets/logo.svg" alt="Angular logo" width="32" height="32" />    </li>    <li>      Dynamic Image:      <img [ngSrc]="logoUrl" [alt]="logoAlt" width="32" height="32" />    </li>    ...  `,  imports: [NgOptimizedImage],})

Add width and height attributes

Note that in the above code example, each image has both width and height attributes. In order to prevent layout shift, the NgOptimizedImage directive requires both size attributes on each image.

In situations where you can't or don't want to specify a static height and width for images, you can use the fill attribute to tell the image to act like a "background image", filling its containing element:
```
      <div class="image-container"> //Container div has 'position: "relative"'  <img ngSrc="www.example.com/image.png" fill /></div>
    
```
Note: For the fill image to render properly, its parent element must be styled with position: "relative", position: "fixed", or position: "absolute".
Prioritize important images

One of the most important optimizations for loading performance is to prioritize any image which might be the "LCP element", which is the largest on-screen graphical element when the page loads. To optimize your loading times, make sure to add the priority attribute to your "hero image" or any other images that you think could be an LCP element.
```
      <img ngSrc="www.example.com/image.png" height="600" width="800" priority />
    
```
Optional: Use an image loader

NgOptimizedImage allows you to specify an image loader, which tells the directive how to format URLs for your images. Using a loader allows you to define your images with short, relative URLs:
```
      providers: [  provideImgixLoader('https://my.base.url/'),]
    
```
Final URL will be 'https://my.base.url/image.png'
```
      <img ngSrc="image.png" height="600" width="800" />
    
```
Image loaders are for more than just convenience--they allow you to use the full capabilities of NgOptimizedImage. Learn more about these optimizations and the built-in loaders for popular CDNs here.

By adding this directive to your workflow, your images are now loading using best practices with the help of Angular 🎉

If you would like to learn more, check out the documentation for NgOptimizedImage. Keep up the great work and let's learn about routing next.

Import the NgOptimizedImage directive

Update the src attribute to be ngSrc

Add width and height attributes

Prioritize important images

Optional: Use an image loader