HP PCL/PJL reference (PCL 5 Color) - Technical Reference Manual

5-26 The PCL Print Model EN
Note Since PCL printers print only at intersections, grid- centered pixel
placement is implemented as shown on the right.
Figure 5-6 Pixel Placement Variations
There are two commands that modify the pixel placement function:
the PCL Pixel Placement command (
?*l#R) and the HP-GL/2 Pixel
Placement command (PP).