Ionic 4 sizing QR CODE?

how to do sizing qr code in ionic4?

already ionic does not make transparent the web view of ionic app and the septum display:none when I start the scan it is possible to decide the dipention of the scan because if I put my view in app.component.html you only see that it is possible to scan also where there is the theme, is there a way to dimension or aggregate the qr code in an element that is not the web view?