Require Certain Size for User Image Upload

Hello!
I am trying to code for a specific image upload size. For example, I only want users to be able to upload images that are 800 x 800 px. Here is a code that I found for a MINIMUM upload size…

add_filter(‘wp_handle_upload_prefilter’,’tc_handle_upload_prefilter’);
function tc_handle_upload_prefilter($file)
{

$img=getimagesize($file[‘tmp_name’]);
$minimum = array(‘width’ => ‘800’, ‘height’ => ‘800’);
$width= $img[0];
$height =$img[1];

if ($width < $minimum[‘width’] )
return array(“error”=>”Image dimensions are too small. Minimum width is {$minimum[‘width’]}px. Uploaded image width is $width px”);

elseif ($height < $minimum[‘height’])
return array(“error”=>”Image dimensions are too small. Minimum height is {$minimum[‘height’]}px. Uploaded image height is $height px”);
else
return $file;
}

But I need this to be equal to 800 x 800 px

Thanks for your help in advance!