Detect an input image is B/W or Grayscale, or color image
B/W image is an image contain all pixel black or white.
Grayscale image is an image contain all pixel has r==g==b (so that B/W actualy is a grayscale image).
Color image is an image is not a grayscale image.
in one pixel r = g = b
float average = (total r value) / totalpixels