picamera2 library basics in Raspberry Pi

Introduction

The picamera2 library helps you take pictures and videos with the Raspberry Pi camera easily.

You want to capture photos with your Raspberry Pi camera.

You want to record videos using the Raspberry Pi camera.

You want to preview what the camera sees on your screen.

You want to control camera settings like brightness or resolution.

You want to build a project that needs camera input, like a security camera.

Syntax

Raspberry Pi

from picamera2 import Picamera2

picam2 = Picamera2()
picam2.start()
image = picam2.capture_array()

picam2.stop()

Always import Picamera2 from the picamera2 library first.

Use start() to begin the camera and stop() to end it.

Examples

Basic example to start the camera, take a picture as an array, then stop the camera.

Raspberry Pi

from picamera2 import Picamera2

picam2 = Picamera2()
picam2.start()
image = picam2.capture_array()
picam2.stop()

This example shows how to configure and start a live preview from the camera.

Raspberry Pi

from picamera2 import Picamera2

picam2 = Picamera2()
preview_config = picam2.create_preview_configuration()
picam2.configure(preview_config)
picam2.start()
# Now you can see the camera preview on screen
picam2.stop()

This example sets up the camera to record video instead of just photos.

Raspberry Pi

from picamera2 import Picamera2

picam2 = Picamera2()
video_config = picam2.create_video_configuration()
picam2.configure(video_config)
picam2.start()
# Record video here
picam2.stop()

Sample Program

This program starts the camera, takes a photo, saves it as a JPEG file, then stops the camera. It uses OpenCV to save the image.

Raspberry Pi

from picamera2 import Picamera2
import cv2

picam2 = Picamera2()
picam2.start()

# Capture one image
image = picam2.capture_array()

# Save the image using OpenCV
image_bgr = cv2.cvtColor(image, cv2.COLOR_RGB2BGR)
cv2.imwrite('captured_image.jpg', image_bgr)

picam2.stop()
print('Image saved as captured_image.jpg')

Important Notes

Make sure your Raspberry Pi camera is enabled in the Raspberry Pi settings before using picamera2.

Use capture_array() to get the image as a NumPy array for easy processing.

Always stop the camera with stop() to free resources.

Summary

picamera2 lets you control the Raspberry Pi camera with simple commands.

You start the camera, capture images or video, then stop it when done.

You can preview, capture photos, or record videos by configuring the camera.

Practice

1. What is the main purpose of the picamera2 library on Raspberry Pi?

easy

A. To control the Raspberry Pi camera for capturing images and videos

B. To manage network connections on Raspberry Pi

C. To program the Raspberry Pi GPIO pins

D. To install software packages on Raspberry Pi

Solution

1. Step 1: Understand the library's purpose

   The picamera2 library is designed specifically to control the Raspberry Pi camera module.

2. Step 2: Compare options with the library's function

   Only To control the Raspberry Pi camera for capturing images and videos correctly describes controlling the camera for images and videos.

3. Final Answer:

   To control the Raspberry Pi camera for capturing images and videos -> Option A

4. Quick Check:

   picamera2 controls camera = B [OK]

Hint: Remember picamera2 is for camera control only [OK]

Common Mistakes:

• Confusing picamera2 with network or GPIO libraries
• Thinking picamera2 installs software
• Assuming picamera2 manages hardware other than camera

2. Which of the following is the correct way to import the picamera2 library in a Python script?

easy

A. from picamera2 import Picamera2

B. from picamera import picamera2

C. import Picamera2

D. import picamera2

Solution

1. Step 1: Recall correct import syntax for picamera2

   The correct class name is Picamera2 and it is imported from the picamera2 module.

2. Step 2: Check each option's syntax

   from picamera2 import Picamera2 uses correct capitalization and syntax: from picamera2 import Picamera2. Others are incorrect due to wrong case or module names.

3. Final Answer:

   from picamera2 import Picamera2 -> Option A

4. Quick Check:

   Correct import = D [OK]

Hint: Remember Python is case-sensitive for imports [OK]

Common Mistakes:

• Using wrong capitalization for Picamera2
• Importing from 'picamera' instead of 'picamera2'
• Trying to import the whole module without class

3. What will the following code print?

from picamera2 import Picamera2
picam2 = Picamera2()
picam2.start()
print(type(picam2))
picam2.stop()

medium

A. Error: Picamera2 not defined

B. <class 'picamera2.Picamera2'>

C. <class 'camera.Picam2'>

D. None

Solution

1. Step 1: Analyze object creation and type

   The code creates an instance of Picamera2 and prints its type, which should be the class picamera2.Picamera2.

2. Step 2: Check for errors or output

   Since the import and instantiation are correct, no error occurs. The printed type matches <class 'picamera2.Picamera2'>.

3. Final Answer:

   <class 'picamera2.Picamera2'> -> Option B

4. Quick Check:

   type(picam2) = <class 'picamera2.Picamera2'> [OK]

Hint: type() shows the object's class with module name [OK]

Common Mistakes:

• Expecting a runtime error due to missing start()
• Confusing class name or module in output
• Thinking print outputs None

4. Identify the error in this code snippet:

from picamera2 import Picamera2
picam2 = Picamera2()
picam2.capture_file('image.jpg')
picam2.stop()

medium

A. No error; code runs fine

B. Wrong method name; should be capture_image()

C. File extension must be .png, not .jpg

D. Missing call to picam2.start() before capture_file

Solution

1. Step 1: Check method usage order

   Before capturing an image, the camera must be started with start(). This code skips that step.

2. Step 2: Verify method names and file formats

   capture_file() is correct method name, and .jpg is a valid extension. So no error there.

3. Final Answer:

   Missing call to picam2.start() before capture_file -> Option D

4. Quick Check:

   start() needed before capture_file() [OK]

Hint: Always start camera before capturing [OK]

Common Mistakes:

• Skipping picam2.start() before capture
• Assuming capture_file() is incorrect method
• Thinking file extension causes error

5. You want to preview the camera feed on screen before capturing a photo using picamera2. Which sequence of commands is correct?

hard

A. picam2 = Picamera2()
picam2.start_preview()
picam2.capture_file('photo.jpg')
picam2.stop()

B. picam2 = Picamera2()
picam2.start()
picam2.preview()
picam2.capture_file('photo.jpg')
picam2.stop()

C. picam2 = Picamera2()
picam2.start()
picam2.start_preview()
picam2.capture_file('photo.jpg')
picam2.stop()

D. picam2 = Picamera2()
picam2.preview()
picam2.capture_file('photo.jpg')
picam2.stop()

Solution

1. Step 1: Understand preview and start sequence

   You must start the camera with start() before previewing. The method to show preview is start_preview().

2. Step 2: Check each option's command order

   picam2 = Picamera2() picam2.start() picam2.start_preview() picam2.capture_file('photo.jpg') picam2.stop() correctly calls start(), then start_preview(), then captures and stops. Others miss start() or use wrong methods.

3. Final Answer:

   picam2 = Picamera2() picam2.start() picam2.start_preview() picam2.capture_file('photo.jpg') picam2.stop() -> Option C

4. Quick Check:

   start() then start_preview() = A [OK]

Hint: Always start() before preview or capture [OK]

Common Mistakes:

• Calling preview without start()
• Using preview() instead of start_preview()
• Not stopping camera after use