// These macros create half circle selections.

  macro "Make right half circle" {
      if (selectionType!=1)
          exit("Elliptical selection required");
      getBoundingRect(x, y, width, height);
      midx = x + width/2;
      getSelectionCoordinates(sx, sy);
      for (i=0; i<sx.length; i++) {
          if (sx[i]<midx) sx[i] = midx;
      }
      makeSelection(3, sx, sy);
  }

  macro "Make left half circle" {
      if (selectionType!=1)
          exit("Elliptical selection required");
      getBoundingRect(x, y, width, height);
      midx = x + width/2;
      getSelectionCoordinates(sx, sy);
      for (i=0; i<sx.length; i++) {
          if (sx[i]>midx) sx[i] = midx;
      }
      makeSelection(3, sx, sy);
  }

  macro "Make bottom half circle" {
      if (selectionType!=1)
          exit("Elliptical selection required");
      getBoundingRect(x, y, width, height);
      midy = y + height/2;
      getSelectionCoordinates(sx, sy);
      for (i=0; i<sy.length; i++) {
          if (sy[i]<midy) sy[i] = midy;
      }
      makeSelection(3, sx, sy);
  }

  macro "Make top half circle" {
      if (selectionType!=1)
          exit("Elliptical selection required");
      getBoundingRect(x, y, width, height);
      midy = y + height/2;
      getSelectionCoordinates(sx, sy);
      for (i=0; i<sy.length; i++) {
          if (sy[i]>midy) sy[i] = midy;
      }
      makeSelection(3, sx, sy);
  }