A fast PCD8544 library (Nokia 5110)

TheCoolest,

This library is just what I need. Adafruit is too heavy and slow. Old hardSPI libraries do not compile on 1.5.2beta. Your library is light and works. But I have few issues.
Could you please help with bitmaps?
First - offsets, I assume second and third argument in bitmap function is X and Y position offsets. It does affect position, but single unit change trow it a few pixels away and large values (like 5) makes it stick to upper left corner. Pretty erratic.
Second - the size. As an example I'm using simple 8x8 bitmap. I did set fourth and fifth arguments to 8.

B11111111,
B00000001,
B00000010,
B00000100,
B00001000,
B00010000,
B00100000,
B11111111,

it does appeared not as Z but as N. OK, it is transposed, but there is always trailing garbage below.

Could you please explain a bit more how to compile bitmap sprites and what exactly arguments for bitmap function do.

Thank you for any help!