Support polycolour QRs

[Noitarud]

Why not have compatibility with multicolour QRs, it will increase data capacity, though exclusive to this app. Here I used paint.net to add colours together, cyan background plus red background equals white. Three will be R+G+B, i will have to think more for more channels since R+Y+Cyan+B won't work well.

My attached GIF image should be scannable with anaglyphic 3D (red/cyan) glasses to separate the layers.

[Noitarud]

As for more, you could have levels, one at 1/3 and another at 2/3 brightness for each colour (sums to 3/3 where both converge), but I have decided greyscale will be best in the long run (but will be difficult if black/white is faded).