reduced usage of magic numbers

[alex-schwartzman]

see title

[josharian]

Do you plan to change the constants?

I'm torn. Although they are much friendly to someone new to the code, I have to admit that I find 270 and 428 a bit more readable than the rather long kCreditCardTargetHeight and kCreditCardTargetWidth. (And if we're going this route, why not 19 and 27 as well?)

I'll defer to @eslav on this, though; I don't feel strongly either way.

[alex-schwartzman]

Sorry, missed numberWidth and numberHeight. Yes, I would replace those numbers by constants as well.

---offtopic---
I recall, when we were programming for i8080, it was really a good idea to use magic numbers, because the assembly code was more readable, and more aligned, but now we have already passed several paradigm shifts away from that mindset. :)
---offtopic---