Through this plugin you can create QR Code images based on your posts’ permalinks and show anywhere in your theme.
Just copy the plugin folder in
wp-content/plugins/ and activate it.
For showing the actuall QR Code you need to use function
show_qr(); provided by this plugin.
or you could just copy the following code into your
single.php file of your theme. Remember this function must be used inside the loop.
If you noticed, there is number (128) which indicates the image size.