This script generates 2d plots using a stepper motor and a webcam

2d_mapper.py

## updated on 26th January 2014
## scans surrounding area and plots x-y points forming a 2d map


import cv2
from numpy import *
import math
import time
import serial
import matplotlib.pyplot as plt

ser = serial.Serial('/dev/ttyUSB1', 9600) 

ser.close()
ser.open()

#variables
loop = 1
dot_dist = 0
count = 0
i = 0
step_num = []
obj_dist = []
x_points = []
y_points = []
angles= []

#cv2.namedWindow("preview")
vc = cv2.VideoCapture(2)

if vc.isOpened(): # try to get the first frame
    rval, frame = vc.read()
	
else:
    rval = False
    #print "failed to open webcam"
	
input("type something and press enter to continue...") ## wait for user input to begin
ser.write('g') ## this tells the pic to start rotating the stepper




while loop == 1:
	
	############Get distance value from camera###############

	#cv2.imshow("preview", frame)
	rval, frame = vc.read()
	key = cv2.waitKey(20)
	if key == 27: # exit on ESC
		loop = 0
	num = (frame[...,...,2] > 245)
	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)	

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

	if tan_theta > 0: # bit of error checking
		obj_dist.append(float(5.33 / tan_theta))## add the latest distance value to obj_dist lsit


		
		
	###### Get stepper value from PIC ####################
	try:
		step_num.append(int(ser.readline())) ## add the latest step value to the ste_num list
	except ValueError:
		pass
		
		
	if (int(ser.readline()) > 2000): ## if a full revolution has occured, stop grabbing frames and process data
		loop = 0

	ser.flushInput()		## prevent the serial receive buffer from being overloaded
	
	print "\033[12;0H" + "the dot is " + str(obj_dist) + "cm  away"

	
ser.write('h')		## sent a 'h' over serial to return the stepper to original position


		

######## Get x-y points from angle and distance information ################


for i in range(len(step_num)): 
	angles.append(step_num[i]*0.176)    ## converting steps into angles in degrees
	

i = 0 
print "len angles : " + str(len(angles)), "count = " +str(count), "length obj_dist = " + str(len(obj_dist))
for i in range(len(angles)): ## getting x-y points from distance and angle information
	x_points.append(obj_dist[i]*(math.cos(math.radians(angles[i])))) 
	y_points.append(obj_dist[i]*(math.sin(math.radians(angles[i]))))

	
plt.plot(x_points,y_points,'ro') ## plot the x-y points
plt.show() ## show the plot