camera_scripts.txt

Raspberry Pi Camera Guide 

 

The examples in this guide are for the Raspberry Pi cameras and USB Webcams and can be used directly with both the Raspberry Pis and the Pis that are on the turtlebot’s. The USB Webcam examples can also be used on the DiCE computers. 

 

Raspberry Pi Camera - command line control 

To test if your camera is connected: -  

$: vcgencmd get_camera 

To capture a picture: 

$: raspistill -o cam.jpg 

https://www.raspberrypi.org/documentation/usage/camera/raspicam/raspistill.md 

To capture a video: 

$: raspivid -o vid.h264 

https://www.raspberrypi.org/documentation/usage/camera/raspicam/raspivid.md 

To view pictures and videos on the RPi: 

gpicview and vlc are both installed and available to use to view pictures and videos respectively 

To export picture and videos: 

scp and/or ftp over to your DICE account or home computer and view from there. 

To stream a video from your RPi: 

$: raspivid -t 0 -l -o tcp://0.0.0.0:3333 

or 

$: raspivid -o - -t 0 -n | cvlc -vvv stream:///dev/stdin --sout '#rtp{sdp=rtsp://:8554/}' :demux=h264 

Note: the second option requires vlc to be installed on your RPi. The Turtlebot RPis do not have vlc installed as part of their default build. 

To view your streamed video: 

VLC - media - open network stream 
tcp/h264://192.168.0.77:3333 

or 

vlc tcp/h264://192.168.0.77:3333 

or 

rtsp://192.168.0.77:8554/ 

 

PiCamera - display camera 

from picamera import PiCamera 
from time import sleep 
 
camera = PiCamera() 
camera.start_preview() 
sleep(5) 
camera.stop_preview() 

 

PiCamera - capture image 

from picamera import PiCamera 
from time import sleep 
 
camera = PiCamera() 
camera.start_preview() 
sleep(5) 
camera.capture('/home/pi/Desktop/image.jpg') 
camera.stop_preview() 

 

PiCamera - record video 

from picamera import PiCamera 
from time import sleep 
 
camera = PiCamera() 
 
camera.start_preview() 
camera.start_recording('/home/pi/Desktop/video.h264') 
sleep(5) 
camera.stop_recording() 
camera.stop_preview() 

 

PiCamera - On Turtlebot - View Camera Feed Using Ros 

In terminal window on robot:- 
$   roslaunch turtlebot3_bringup turtlebot3_rpicamera.launch 
In terminal window on DiCE:- 
$  rqt_image_view 

 

To view the USB webcam 

ls /dev 

On the standalone RPis, the USB webcam should appear as video1. On the Turtlebot RPis,it should appear as video0. 

vlc 

Media - open_capture_device 
Video device name = video0 or video1 (refer to note above) 
Video standard = All 

 

USB webcam - capture image 

Using pygame 

import pygame 
import pygame.camera 
 
pygame.camera.init() 
pygame.camera.list_cameras() # Camera detected or not 
cam = pygame.camera.Camera("/dev/video1", (640,480)) 
cam.start() 
img = cam.get_image() 
pygame.image.save(img, "filename.jpg") 

Display webcam video 

Note: VNC needs to be enabled on RPi, and code should be run from a VNC connection. 

Using OpenCV 

import cv2 
 
cap = cv2.VideoCapture("/dev/video1") 
 
# Check if the webcam is opened correctly  
if not cap.isOpened(): 
  raise IOError("Cannot open webcam") 
 
while True: 
  ret, frame = cap.read() 
  frame = cv2.resize(frame, None, fx=1, fy=1, interpolation=cv2.INTER_AREA) 
  cv2.imshow('Input', frame) 
 
  c = cv2.waitKey(1) 
  if c == 27: 
    break 
 
cap.release() 
cv2.destroyAllWindows() 

Using pygame 

import pygame 
import pygame.camera 
from pygame.locals import * 
 
DEVICE = '/dev/video1' # video0 if using Turtlebot 
SIZE = (640, 480)  
FILENAME = 'capture.png' 
 
def camstream(): 
  pygame.init() 
  pygame.camera.init() 
  display = pygame.display.set_mode(SIZE, 0) 
  camera = pygame.camera.Camera(DEVICE, SIZE) 
  camera.start() 
  screen = pygame.surface.Surface(SIZE, 0, display) 
  capture = True 
  while capture: 
    screen = camera.get_image(screen) 
    display.blit(screen, (0,0)) 
    pygame.display.flip() 
    for event in pygame.event.get(): 
      if event.type == QUIT: 
        capture = False 
      elif event.type == KEYDOWN and event.key == K_s: 
        pygame.image.save(screen, FILENAME) 
  camera.stop() 
  pygame.quit() 
 
if __name__ == '__main__': 
  camstream() 

 

Capture webcam stream 

Using OpenCV 

import numpy as np 
import cv2 
 
cap = cv2.VideoCapture("/dev/video1") # video0 if using Turtlebot 
 
# Define the codec and create VideoWriter object 
fourcc = cv2.VideoWriter_fourcc('XVID') 
out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640,480)) 
 
while cap.isOpened(): 
  ret, frame = cap.read() 
  if ret == True: 
    frame = cv2.flip(frame, 0) 
 
    # Write the flipped frame 
    out.write(frame) 
 
    cv2.imshow('frame', frame) 
    if cv2.waitKey(1) & 0xFF == ord('q'): 
      break 
  else: 
      break 
 
# Release everything if job is finished 
cap.release() 
out.release() 
cv2.destroyAllWindows()