QR Redirector lets you create a QR code for a URL on your site, and redirect that URL anywhere. The result is a reusable QR Code.
Use the following shortcode:
where id is the post ID of your QR Redirect post. This shortcode will be generated on the edit page for each of your QR Redirects for you to copy and paste.
No. The QR Code points to a WordPress permalink on your site. The only time you would ever have to switch out an image is if you change your site's permalink settings, and thus change the permalinks of the QR Redirect posts. Presumably this is something you won't be doing too often, if ever.
A new image with the appropriate settings will be generated and the original image will be removed from your site. Any shortcodes in use on your site will be automatically updated. Printed versions of the old image will still function, but if you were hotlinking the original image somewhere outside of your website you will need to update it there. If you have previously uploaded to old image to another site, rather than hotlinking, it will still function.
QR Codes on their own are static. In order to update them, you have to generate a whole new image (which would suck if you were putting them on flyers or some other printed medium and suddenly needed to change them). This plugin lets you point your QR code's embeded URL to a different web address if you need to.
For example, if you are using an off-site service to host a contest, you can point a QR code at that site for the duration of the contest and later change it to point to another page with the contest winners.
Using the PHPQRCode library by Dominik Dzienia. This is PHP implementation of QR Code 2-D barcode generator. It is pure-php LGPL-licensed implementation based on C libqrencode by Kentaro Fukuchi.
For more information, see: http://phpqrcode.sourceforge.net/
Largely because of the new way in which the QR codes are generated. Users would have had to resave all of their old QR Redirect posts in order to generate the new images. This didn't seem very user friendly to me.
Additionally, not everyone may want to host QR images on their own site. The old plugin will continue to function until Google removes the QR functionality from its Charts API. I decided that this would be a good way to give people the option of hosting the images themselves, or letting Google do it for them.