// This macro demonstrates how to retrieve the scale of the  active image

  var scale, unit;

  getScaleAndUnit();
  print("Scale: "+scale+" pixels per "+unit);  

  // Sets the global variables 'scale' and 'unit' based on the 'Resolution: '
  // line from the active images 'Show Info' string. 
  function getScaleAndUnit() {
      selectImage(getImageID);
      info = getInfo();
      index1 = indexOf(info, "Resolution: ");
      if (index1==-1)
          {scale=1; unit = "pixel"; return;}          
      index2 = indexOf(info, "\n", index1);
      line = substring(info, index1+12, index2);
      words = split(line, "");
      scale = 0+words[0];
      unit = words[3];
  }