# for loop to iterate the x,y,width and height of the face
for (x,y,w,h) in faces:
    #draw rectangle using x,y,width+x and height+y
    cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)
    #The ROI is set using the relevant x,y width and height coodinates
    roi_gray = gray[y:y+h, x:x+w]
    # Same is done for the color region of interest
    roi_color = img[y:y+h, x:x+w]

    # global var:
    eye_counter = 0
    # eyes variable is set with module to detect eyes
    eyes = eye_cascade.detectMultiScale(roi_gray)

    # for loop to iterate through the x,y,width,height of the eyes
    for (ex, ey, ew, eh) in eyes:
        # ROI is determined from y value found between the other y value.
        # ey:ey + h means eye(Y value) between eye(Y value) plus the eye height.
        # The : is a slicing operator which means between in this context.
        roi_color_eye = roi_color[ey:ey + eh, ex:ex + ew]
        # write the ROI to image and counter is included so that the new JPG will be numbered acordingly.
        # E.g on first iteration, eye_0.jpg will be written, then eye_1.jpg second iteration.
        cv2.imwrite("eye_%d.jpg" % eye_counter, roi_color_eye)
        # increment the counter
        eye_counter += 1
        # draw rectangle around area of interest which is equal to the eye x,y,width,height coodinates.
        cv2.rectangle(roi_color, (ex, ey), (ex + ew, ey + eh), (0, 50, 0), 2)