void NumbPadToPixel(int ich, int side, int *ipx, int *ipz)
{
/* ich should be  0,1,2 for PC1,2,3 */
  const int wire_adjust[3]={0,-1,1};
  int tempx,tempz;

/* first go from padx,padz space: for one side of one sector in chamber ich
PC1: (0,19)x(0,107) to wire,z pad-space (-1,58)x(-1,106) 
      (which in fact gives cell-space correctly (0,57)x(0,105) ..) 
PC2/3: (0,39)x(0,107) to wire,z pad-space (-1,116)x(-1,106) 
      (which in fact gives cell-space correctly (0,115)x(0,105) ..) */

  tempz=*ipz-1;
  tempx = 3*(*ipx%20)+wire_adjust[(tempz+3)%3];

/* tempx,tempz are now true within all chamberhalves..  Now transform to
north side coordinate system*/
  if (ich==0) { /* PC1 (-1,58)x(-1,106-1+107)) = (-1,58)x(-1,212) cells: (0,57)x(0,211) */
    if (side==0) { /* South */
       tempx=57-tempx; 
       tempz=105-tempz;  
    }
    else tempz=tempz+106; /* North */
   }

  if ((ich == 1) || (ich == 2)) { /* PC2,3 (-1,58-1+59)x(-1,212) = (-1,116)x(-1,212) cells: (0,115)x(0,211) */
     if  (*ipx>=20)  tempx=tempx+58; /* 2nd module */
     if (side==0) { /* South */
          tempx=115-tempx;
          tempz=105-tempz;
     }
     else tempz=tempz+106; /* North */
  }

/* and the final twist: PC2 is oriented with the MB towards IP. If we flip the 
wire direction, it will follow the same standard as the rest: z in the z 
direction (..) and wire following the phi direction */
  if (ich == 1) { /* PC2 */
    tempx=115-tempx; 
  }

  *ipx = tempx;
  *ipz = tempz;
}

And here's the more dense version..

void NumbPadToPixel(int ich, int side, int *ipx, int *ipz)
{
/* ich should be  0,1,2 for PC1,2,3 */
  const int wire_adjust[3] = {0,-1,1};
  const int cells_along_wire = 106; /* Number of cells along wire for half a sector(PC1:subsector) */
  const int cells_across_wire[3] = {58,116,116}; /* Number of cells across wire for a sector(PC1:subsector) */
  int tempx,tempz;

  tempz=*ipz-1;
  tempx = 3*(*ipx%20)+wire_adjust[(tempz+3)%3] + (*ipx/20)*58;

/* tempx,tempz are now true within all chamberhalves..  Now transform to
north side coordinate system*/

  if (side==0) { /* South */
     tempx=(cells_across_wire[ich]-1)-tempx; 
     tempz=(cells_along_wire-1)-tempz;  
  }
  else tempz=tempz+cells_along_wire; /* North */

  if (ich == 1) { /* PC2 */
    tempx=(cells_across_wire[ich]-1)-tempx; 
  }

  *ipx = tempx;
  *ipz = tempz;
}