$middle_y = ($canvas_h / 2) - $overlay_h; // $canvas_h is the original picture height, $overlay_h is the overlay height
$middle_x = ($canvas_w / 2) - $overlay_w; // $canvas_w is the original picture width, $overlay_w is the overlay width
imagecopymerge($canvas_img, $overlay_img, $middle_x,$middle_y,0,0, $overlay_w, $overlay_h, $Opacity);
Now, I want to center the overlay over the image...and I thought my math logic would/should work, but it does not.
And also, a function that will generate a thumbnail as well, but portioned to size, so it does not appear distorted.