在AJAX中将图像发布到PHP

I would like to send an image to a php file using AJAX.

Here's my JS code:

$.ajax({
    type: "POST",
    url: "http://website.com/add-image.php",
    data: "img=" + img
})

And That's my PHP

<?php
if ( !empty( $_POST["img"] ) )
{
    move_uploaded_file( $_POST["img"], "image.png" );
}
?>

but it doen't work.

I also tried to replace move_uploaded_file by imagepng or imagejpg but still no result.

How can I save the image on my server ? Thanks