Prevent generating oversized media in spatie media library

I am using Spatie media library to manage media in my laravel app. The issue is it generates oversized images even if the uploaded file is small which results in pixelated images.

Below is my model code. Suppose if I upload image of width 700 pixels, it also generates md, lg, and xl images.

How do I prevent media conversions which are greater than the uploaded image's width?

namespace App;

use Illuminate\Database\Eloquent\Model;
use Spatie\Image\Manipulations;
use Spatie\MediaLibrary\HasMedia;
use Spatie\MediaLibrary\InteractsWithMedia;
use Spatie\MediaLibrary\MediaCollections\Models\Media; 

class Post extends Model implements HasMedia
{
    use InteractsWithMedia;

    public function registerMediaConversions(Media $media = null) : void
    {
        $this->addMediaConversion('thumb')
            ->width(100);
        $this->addMediaConversion('xs')
            ->width(320);
        $this->addMediaConversion('sm')
            ->width(640);
        $this->addMediaConversion('md')
            ->width(768);
        $this->addMediaConversion('lg')
            ->width(1024);
        $this->addMediaConversion('xl')
            ->width(1280);
    }

    public function registerMediaCollections() : void
    {
        $this->addMediaCollection('images');
    }
}