[nickdigger]

here you go:

//byte row_offsets is unused
byte dr = 0x80 + x + (y&1 ? 0x40 : 0) + (y&2 ? 0x14 : 0);
//32 bytes saved (burp)


edit: this one appears to save 18 more:

byte dr = 0x80 + x;
if (y&1) dr+= 0x40;
if (y&2) dr+= 0x14;