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5)QR code creation and recognition
5.QR code creation and recognition
1. QR code
1.1. Introduction to QR code
QR code is a type of two-dimensional barcode. QR comes from the abbreviation of "Quick Response" in English, which means quick response. It comes from the inventor's hope that the content of QR code can be decoded quickly. QR code not only has large information capacity, high reliability, and low cost, but can also represent various text information such as Chinese characters and images. It has strong confidentiality and anti-counterfeiting and is very convenient to use. What's more important is that the QR code technology is open source.
1.2. Structure of QR code
| Pic | Analysis |
|---|---|
 | Positioning markings: Indicate the direction of the QR code. |
 | Alignment markings: If the QR code is large, these additional elements help with positioning. |
 | Timing pattern: Through these lines, the scanner can identify how big the matrix is. |
 | Version information: This specifies the version number of the QR code being used. There are currently 40 different versions of QR codes. Versions used in the sales industry are usually 1-7. |
 | Format information: The format pattern contains information about error tolerance and data masking patterns and makes scanning the code easier. |
 | Data and error correction keys: These modes hold the actual data. |
 | Quiet zone: This area is very important for the scanner, as its function is to separate itself from the surrounding areas. |
1.3. Features of QR code
The data values in the QR code contain repeated information (redundant values). Therefore, even if up to 30% of the QR code structure is destroyed, the readability of the QR code is not affected. The storage space of QR code is up to 7089 bits or 4296 characters, including punctuation marks and special characters, which can be written into QR code. In addition to numbers and characters, words and phrases (such as web addresses) can also be encoded. As more data is added to the QR code, the code size increases and the code structure becomes more complex.
1.4. QR code creation and recognition
1. Source code path
/root/yahboomcar_ros2_ws/yahboomcar_ws/src/yahboomcar_visual/simple_qrcode
2.Installation package
xxxxxxxxxxpython3 -m pip install qrcode pyzbarsudo apt-get install libzbar-dev
The factory docker image has been installed.
3.Create QRcode_Create.py
Enter docker, open the terminal and enter,
xcd /root/yahboomcar_ros2_ws/yahboomcar_ws/src/yahboomcar_visual/simple_qrcode/python QRcode_Create.py
After the program is run, you will be prompted to enter the generated content, and press Enter to confirm the content. Here we take creating the "yahboom" string as the content as an example,
Take out your phone and try to scan the QR code that appears on the right. The scan result will be the characters yahboom.
Source code analysis,
xxxxxxxxxx#Create qrcode objectqr = qrcode.QRCode( version=1, error_correction=qrcode.constants.ERROR_CORRECT_H, box_size=5, border=4,)#Meanings of each parameter'''version：An integer with a value from 1 to 40, controlling the size of the QR code (the minimum value is 1, which is a 12×12 matrix). If you want the program to determine this automatically, set the value to None and use the fit argument.error_correction：Controls the error correction function of QR codes. Possible values are the following 4 constants. ERROR_CORRECT_L：About 7% or less of errors can be corrected. ERROR_CORRECT_M（Default): Approximately 15% or less of errors can be corrected. ROR_CORRECT_H：About 30% or less of errors can be corrected.box_size：Control the number of pixels contained in each small grid in the QR code.border：Control the number of cells included in the border (the distance between the QR code and the image border) (the default is 4, which is the minimum value specified by relevant standards)'''#Add logo to qrcode QR codemy_file = Path(logo_path)if my_file.is_file(): img = add_logo(img, logo_path)#Add dataqr.add_data(data)# Data input# fill dataqr.make(fit=True)# Generate pictures# generate imagesimg = qr.make_image(fill_color="green", back_color="white")4. Identify QRcode_Parsing.py
Enter docker, open the terminal and enter,
xxxxxxxxxxcd /root/yahboomcar_ros2_ws/yahboomcar_ws/src/yahboomcar_visual/simple_qrcode/python QRcode_Parsing.py
After the program is run, we place the QR code in front of the camera. The program will recognize the content of the QR code, mark it on the picture and print out the recognized content on the terminal.
Source code analysis,
xxxxxxxxxxdef decodeDisplay(image, font_path): gray = cv.cvtColor(image, cv.COLOR_BGR2GRAY) # It is necessary to convert the output Chinese characters into Unicode encoding form first. barcodes = pyzbar.decode(gray) for barcode in barcodes: # Extract the position of the bounding box of the QR code (x, y, w, h) = barcode.rect # Draw the bounding box of the barcode in the image cv.rectangle(image, (x, y), (x + w, y + h), (225, 0, 0), 5) encoding = 'UTF-8' # To draw it, you need to convert it into a string first barcodeData = barcode.data.decode(encoding) barcodeType = barcode.type # Plot data and types on the image pilimg = Image.fromarray(image) # Create brushes draw = ImageDraw.Draw(pilimg) # Parameter 1: font file path, parameter 2: font size fontStyle = ImageFont.truetype(font_path, size=12, encoding=encoding) #Parameter 1: print coordinates, parameter 2: text, parameter 3: font color, parameter 4: font draw.text((x, y - 25), str(barcode.data, encoding), fill=(255, 0, 0),font=fontStyle) #PIL image to cv2 image image = cv.cvtColor(np.array(pilimg), cv.COLOR_RGB2BGR) # Print barcode data and barcode type to terminal print("[INFO] Found {} barcode: {}".format(barcodeType, barcodeData)) return image