Detecting coloured QR Codes

[Mamonaku]

Hello,
thanks for such great code!
I'm having troubles detecting QR code that are not in black and white - I paid attention to have contrasting colours though - and also checking those QR code using app available from the app store. With the later, QR codes are identified without issues.

With QRCodeReader however, it doesn't work. At first I though it was a contrast problem, but it turns out that it often works when increasing the distance between the camera and the code.

to replicate this problem, you can do the following:
use 1.png (orange) it isn't always detected. In such case move the camera further back... (note that too far back and you'll detect the one below)
use 2.png, always detected.

What can be done to improve the detection ?
thanks!