I recently encountered an issue within WordPress for my website Smooth Web Hosting. No matter what I tried, even if I saved the image as the correct size, WordPress would always prompt me to crop the image I used for my site logo (within Customise -> Site Identity). This would result in the image being displayed with lower quality than it should.
Here is some code that you can add to your functions.php file (I strongly recommend creating a child theme and adding it to that instead of your main theme files) which will let you skip the logo cropping stage in WordPress:
function logo_size_change(){
remove_theme_support( 'custom-logo' );
add_theme_support( 'custom-logo', array(
'height' => 82,
'width' => 240,
'flex-height' => true,
'flex-width' => true,
) );
}
add_action( 'after_setup_theme', 'logo_size_change', 11 );
Be sure to change the height and width figures to your desired size.