Bug in BMP padding calculation when pixelsPerModule is odd

[KrisVandermotten]

BitmapByteQRCode.GetGraphic uses the following formula to calculate the number of padding bytes per row:

var paddingLen = sideLength % 4;

That's not correct. It happens to work when sideLength is even, i.e. when pixelsPerModule is even, but it fails when sideLength is odd.

The correct formula would be (4 - (sideLength % 4)) % 4, or the more efficient equivalent -sideLength & 3.

[KrisVandermotten]

Hmmm, it looks like the code may have been correct after all, albeit in a non-obvious way.

Indeed, sideLength is the number of pixels, not the number of bytes in a pixel row. That needs to be multiplied by 3 to obtain the number of bytes. That multiplication by 3 saves the day.

sideLength % 4	(sideLength % 4) * 3	((sideLength % 4) * 3) % 4
0	0	0
1	3	3
2	6	2
3	9	1

Sorry about that.

[Shane32]

No problem and thanks for looking into it!