// This macro draws the Feret diameter of the current area selection.
  
  macro "Draw Feret" {
     requires("1.43a");
     if (selectionType==-1)
         exit("Area selection required");
     List.setMeasurements;
      length = List.getValue("Feret");  
     x1 = List.getValue("FeretX");
     y1 = List.getValue("FeretY");
     angle = List.getValue("FeretAngle");
     drawFeret(x1, y1, angle, length);
  }

  function drawFeret(x1, y1, angle, length) {
     if (angle<=90)
        angle = -angle;
     else
        angle  = 180-angle;
     angle = angle*(PI/180);
     getVoxelSize(w, h, d, unit);
     if (w!=h)
        exit("Square pixels required");
     x1 /= w;
     y1 /= h;
     length /= w;
     x2 = x1 + length*cos(angle);
     y2 = y1 + length*sin(angle);
     drawLine(x1, y1, x2, y2);
  }