Introduction

Hello and Welcome to the Part 1 blog of 96Boards Photobooth project. This fun intented project kicked off with an Introductory blog last week and today I have arrived with an update on its progress. As like the previous blog series, I have partitioned this project into series of blog for reporting the progress and at the end of this project, the complete source code will be hosted at the 96Boards Org repository along with the instructions for recreation.

Part 1 - 96Boards Photobooth

In this Part 1 blog, we will see how to do image capturing using Dragonboard410c interfaced with OV5640 camera sensor with the help of D3 Camera Mezzanine. Image capturing is the first step for this Photobooth project and it involves the use of OpenCV.

Flashing Boot and Rootfs images

First and foremost we need to prepare the boot image and Root file system for the Dragonboard410c inorder to interface it with D3 Camera Mezzanine and OV5640 camera sensor. For making the life easier, we are going to use the custom boot image and Root file system provided by D3 Engineering. These images can be downloaded from below links:

After downloading the images, flash it onto Dragonboard and setup the Camera Mezzanine using the instructions available in D3 Engineering Wiki.

Note: The custom images were based on 4.9 QC release kernel and it is a bit outdated.

Once the Dragonboard410c is setup with the required boot and rootfs images, verify the functionality of the camera by using the scripts mentioned in the Wiki.

Installing OpenCV

Next step is to install OpenCV on Dragonboard410c. All of the instructions are available in the Projects Org, just follow it for installing OpenCV. Only change required is to replace the cmake command with below one:

$ cmake -D CMAKE_BUILD_TYPE=RELEASE -DWITH_LIBV4L=ON -DWITH_GSTREAMER=ON -DWITH_OPENCL=ON -DBUILD_EXAMPLES=OFF -DBUILD_opencv_apps=OFF -DBUILD_DOCS=OFF -DBUILD_PERF_TESTS=OFF -DBUILD_TESTS=OFF -DCMAKE_INSTALL_PREFIX=/usr/local -DENABLE_PRECOMPILED_HEADERS=OFF -DOPENCV_EXTRA_MODULES_PATH=<opencv_contrib>/modules ../

Installing MRAA

MRAA library is used for accessing the peripherals on 96Boards CE platforms. In this project, we will be using this library for interfacing the push button to GPIO.

Follow the instructions here for installing mraa library on Dragonboard410c.

Image capturing using OpenCV

Once OpenCV and MRAA libraries are installed, we can proceed to capturing an image.

Hardware setup

Make sure Dragonboard410c is turned off
Connect OV5640 to D3 Camera Mezzanine
Place D3 Camera Mezzanine on top of Dragonboard
Connect Linksprite LCD screen to Dragonboard
Connect a Push button to Pin 2 of J5 connector on Camera Mezzanine
Power on Dragonboard using compatible power supply

Note: Push button can be connected in both Pull up/down mode.

Setup the media pipeline by executing below commands:

$ sudo media-ctl -d /dev/media1 -l '"msm_csiphy0":1->"msm_csid0":0[1],"msm_csid0":1->"msm_ispif0":0[1],"msm_ispif0":1->"msm_vfe0_rdi0":0[1]'
$ sudo media-ctl -d /dev/media1 -V '"ov5640 1-0078":0[fmt:UYVY8_2X8/1920x1080 field:none],"msm_csiphy0":0[fmt:UYVY8_2X8/1920x1080 field:none],"msm_csid0":0[fmt:UYVY8_2X8/1920x1080 field:none],"msm_ispif0":0[fmt:UYVY8_2X8/1920x1080 field:none],"msm_vfe0_rdi0":0[fmt:UYVY8_2X8/1920x1080 field:none]'

Now, execute the following python script to capture image after a button press:

import numpy as np
import cv2
import time
import os
import mraa

pressed = False
count = 1

# Set CSI camera as the default one for V4L2
os.system("v4l2-ctl -d /dev/video0")

# Initialize OpenCV video capture
cap = cv2.VideoCapture(0)
cv2.namedWindow('96Boards Photobooth', cv2.WINDOW_NORMAL)
cv2.resizeWindow('96Boards Photobooth', 800, 480)

def putText(img, text, x, y):
    colour = (255, 255, 255)
    font = cv2.FONT_HERSHEY_COMPLEX
    cv2.putText(img, text, (x, y), font, 7, colour, 4)

def capture_and_show(text, x, y):
    ret, frame = cap.read()
    putText(frame, text, x, y)
    cv2.imshow('96Boards Photobooth', frame)

def capture_and_store():
    global count
    ret, frame = cap.read()
    cv2.imwrite("user_" + str(count) + ".jpg", frame)
    count += 1

def button_callback(button):
    global pressed
    pressed = True

def countdown():
    global cap
    for x in range(5, 0, -1):
        capture_and_show(str(x), 900, 600)
        cv2.waitKey(20)
        time.sleep(1)

# Initialize push button
button = mraa.Gpio(24);
button.dir(mraa.DIR_IN)
button.isr(mraa.EDGE_BOTH, button_callback, button)

while 1:
    # Show live preview
    capture_and_show("TAKE", 570, 600)
    if cv2.waitKey(20) & 0xFF == ord('q'):
        break

    # Button pressed
    if pressed==True:
	# Initiate countdown
        countdown()
	# Capture the image
        capture_and_show("CHEESE", 500, 600)
        time.sleep(1)
        capture_and_store()
        captured = cv2.imread("/home/linaro/Documents/photobooth/user_" + str(count - 1) + ".jpg")
	# Show the image preview
        cv2.imshow("96Boards Photobooth", captured)
        cv2.waitKey(20)
        time.sleep(2)
        pressed = False

# Do cleanup
cap.release()
cv2.destroyAllWindows()

Expected workflow after executing the above script:

Camera shows the live preview in the screen with TAKE text at the center
User presses the push button
Counter starts from 5 and decrements at 1 second interval
When the counter decrements to 0, CHEESE will be displayed and the image will be captured and stored as user_x.jpg (x stands for person count)

Video Demonstration

Conclusion

So, with the above steps we can capture an image upon the user request with a countdown timer and store it in the same directory. This demostrates how easy is it to interface camera sensor with Dragonboard410c.

In the next blog, we will see how to apply Snapchat like filters with several options to choose from. This will make the photobooth more fun to play with.