answer to that would depend on the apk you're usingwhere is the actual QR code stored in the app ? its not the same one that is in the res/drawable folder thats what i could not work out the location
bcos anyone with the know how can easily point the app to call qrcode image from almost anywhere that's "allowed/useable" by the app.... even with a "webview" so the image can be changed anytime remotely via panel or php
so obviously if the apk you're using has been edited by someone else to use different values other than the "typical/usual" image_qrcode.png then just look in the layout xml holding the item you're interested in and you'll find pointers/hint of the item's possible location
example, a quick look in the apk in the main post of this thread n you'll find that the image taking the "onscreen position" of the qrcode imageview is actually drawable/logo.jpg (the ftg logo) and not image_qrcode.png as seen "typically" in ibo