* Ensure QR codes have a border large enough
(The QR code spec requires a border at least 4*box_size thick but we can't
just set border=16 because that results in a QR code more than 255px tall
and I'm not yet ready to use fullimage() as a backend for it)
This fix was originally commited by Stephan Sokolow on 2014-05-22
* Let the user print stuff using qr example
* fix tests
- ported test cases for EscposImage class, copied over 1px and 2px test images from escpos-php
- added test cases over image print function
- updated QR tests to also include image output check
- updated CLI to match new image function options
Expand settings on escpos.qr to include ec, size,
model and 'native' (send image or send esc/pos QR command).
Default is set as native=False, so existing code will continue to
render QR codes as images.
Romain Porte