I'm trying to add a QR image to the POS's receipt. The code I used in a normal invoice that worked was the following one:

<img t-att-src="'/report/barcode/?type=%s&amp;value=%s&amp;width=%s&amp;height=%s'%('QR', o.qr_code_string, 150, 150)"/>

For the receipt, I exported for printing my string as receipt.qr_string and added the following line to the receipt's inheriting XML file:

<img t-att-src="'/report/barcode/?type=%s&amp;value=%s&amp;width=%s&amp;height=%s'%('QR', receipt.qr_string, 150, 150)"/>

But the image appear like a broken link. How do I achieve this?