The Raspberry Pi camera module can take picture when a motion occurs, so you can use it for surveillance purposes. Here is how this can be done:

1. First, make sure that your Raspberry Pi is running the latest firmware by running the command:

sudo rpi-update

2. If not already installed, install the picamera python module by using this command:

sudo apt-get install python-picamera

3. You will also need to install Python Imaging Library (PIL) to add image processing capabilities to your Python interpreter. This can be done by running this command:

sudo apt-get install python-imaging-tk

4. Now that the software required is installed you’ll need to create your Python script, copy the following code into a file called “motion.py”, either by using Nano or a text editor in the GUI:

import io
import os
import picamera
import time
from datetime import datetime
from PIL import Image

camera = picamera.PiCamera()

difference = 20
pixels = 100

width = 1280
height = 960

def compare():
	camera.resolution = (100, 75)
	stream = io.BytesIO()
	camera.capture(stream, format = 'bmp')
	stream.seek(0)
	im = Image.open(stream)
	buffer = im.load()
	stream.close()
	return im, buffer
def newimage(width, height):
	time = datetime.now()
	filename = 'motion-%04d%02d%02d-%02d%02d%02d.jpg' % (time.year, time.month,time.day, time.hour,time.minute, time.second)
	camera.resolution = (width, height)
	camera.capture(filename)
	print 'Captured %s' % filename
image1, buffer1 = compare()

timestamp = time.time()

while (True):
	image2, buffer2 = compare()

	changedpixels = 0
	for x in xrange(0, 100):
		for y in xrange(0, 75):
			pixdiff = abs(buffer1[x,y][1]- buffer2[x,y][1])
			if pixdiff > difference:		
				changedpixels += 1
	if changedpixels > pixels:
		timestamp = time.time()
		newimage(width, height)
	image1 = image2
	buffer1 = buffer2

Be sure to get the right indentation of the code.

5. The Python script will need to be executable, that’s done by the following command:

chmod +x motion.py

6. And finally, run the script with the command:

python motion.py

Your Raspberry Pi should now detect motion and take a picture every time it happens.