#define SETPIXEL(op, v) { \
switch (npixels++ & 3) { \
#define SETPIXEL(op, v) { \
switch (npixels++ & 3) { \
case 1: op[0] |= (v) << 4; break; \
case 2: op[0] |= (v) << 2; break; \
case 3: *op++ |= (v); break; \
case 1: op[0] |= (v) << 4; break; \
case 2: op[0] |= (v) << 2; break; \
case 3: *op++ |= (v); break; \