Not really sure what exactly are you trying to achieve here by doing this.
But FileReader accepts blobs, as an argument to readAsDataURL. So you'll have to read it from the URL using HttpClient's get method specifying responseType as blob. The onload method on the reader can then be used to get the Base 64 url for the image.
Here, give this a try:
import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
name = 'Angular';
constructor(private http: HttpClient) { }
ngOnInit() {
this.http.get('https://avatars0.githubusercontent.com/u/5053266?s=460&v=4', { responseType: 'blob' })
.subscribe(blob => {
const reader = new FileReader();
const binaryString = reader.readAsDataURL(blob);
reader.onload = (event: any) => {
console.log('Image in Base64: ', event.target.result);
};
reader.onerror = (event: any) => {
console.log("File could not be read: " + event.target.error.code);
};
});
}
}
Here's a Working Sample StackBlitz for your ref.