Laser_detection

## program written by Shane Ormonde 7th sept 2013
## updated on 25th January 2014
## calculates the distance of a red dot in the field of view of the webcam.
import cv2
from numpy import *
import math

#variables
loop = 1
dot_dist = 0

cv2.namedWindow("preview")
vc = cv2.VideoCapture(0)

if vc.isOpened(): # try to get the first frame
    rval, frame = vc.read()

else:
    rval = False
    #print "failed to open webcam"

if rval == 1 :

    while loop == 1:
        cv2.imshow("preview", frame)
        rval, frame = vc.read()
        key = cv2.waitKey(20)
        if key == 27: # exit on ESC
            loop = 0
        num = (frame[...,...,2] > 236)
        xy_val =  num.nonzero()

        y_val = median(xy_val[0])
        x_val = median(xy_val[1])

        #dist = ((x_val - 320)**2 + (y_val - 240)**2 )**0.5 # distance of dot from center pixel
        dist = abs(x_val - 320) # distance of dot from center x_axis only

        print(" dist from center pixel is " + str(dist))

        # work out distance using D = h/tan(theta)

        theta =0.0011450*dist + 0.0154
        tan_theta = math.tan(theta)

        if tan_theta > 0: # bit of error checking
            obj_dist =  int(5.33 / tan_theta)

        print("the dot is " + str(obj_dist) + "cm  away")
elif rval == 0:
    print(" webcam error ")