// Save this file in the plugins folder as
// "Calculate_Black_to_White_Ratio.txt"
// and restart ImageJ to create a
// "Calculate Black to White Ratio" command.

  requires("1.32g");
  if (bitDepth!=8)
      exit("This macro requires an 8-bit image");
  black = 0;
  white = 255;
  getHistogram(0, hist, 256);
  total = 0;
  for (i=0; i<256; i++)
      total += hist[i];
  print("");
  print("Black pixels: " + hist[black]);
  print("White pixels: " + hist[white]);
  print("Percent black:" +100*hist[black]/total);
  print("Percent white:" +100*hist[white]/total);
  print("Black/white ratio: " + hist[black]/hist[white]);