Upload image to AWS S3 - resize problem

Hello , for few days i'm struggling to upload a file to aws. The problem it's not that i cannot upload it , it's that i cannot resize it in order to make it smaller.I've read that a good tool for this job is Image Intervention so i used it but it's not doing what it must. Here you have my store method from the controller :

$this->validate($request, [
        'buletin' => 'mimes:jpeg,jpg,png,bmp',
        'factura' => 'mimes:jpeg,jpg,png,bmp',
        'card' => 'mimes:jpeg,jpg,png,bmp',
    ]);
    $s3 = Storage::disk('s3');
    $username = $request->input('username'); // this is the username which uploaded the file , as i dont use authentication system it's a hidden filed

    //here i take the image , resize it and upload it to S3
    $img = Image::make($request->file('buletin'))->encode('png')->resize(1024,768);
        $fileFileName = $username . '_buletin';
        $filePath = '/'.$username.'/' . $fileFileName;
        $s3->put($filePath, (string)$img);

My big problem is that the user cand come and upload a 5 , 10 ,100 mb image , and i don't want to store such a huge file.

If you have any suggestions about how to handle this kind of image upload , maybe with an other package please advise.

Do you think it's a good option to upload the image directly from the request to aws ?

Thank you