Barcode Recognition Routine Explanation#

Overview#

A Barcode is a visual pattern used to represent data, encoding information through stripes or patterns of varying widths and spacings. Barcodes are widely used across various industries for automatic identification, storage, and management of data.

CanMV supports the OpenMV algorithm and can recognize barcodes. The relevant interface is find_barcodes, which supports multiple barcode formats.

Example#

This example sets the camera output to a 640x480 grayscale image and uses image.find_barcodes to recognize barcodes.

Tip

If the recognition success rate is low, try adjusting the camera’s mirror and flip settings, and make sure to leave a white area on both sides of the barcode.

# Barcode detection example
import time
import math
import os
import gc
import sys

from media.sensor import *
from media.display import *
from media.media import *

# Function: Get the name of the barcode type
def barcode_name(code):
    barcode_types = {
        image.EAN2: "EAN2",
        image.EAN5: "EAN5",
        image.EAN8: "EAN8",
        image.UPCE: "UPCE",
        image.ISBN10: "ISBN10",
        image.UPCA: "UPCA",
        image.EAN13: "EAN13",
        image.ISBN13: "ISBN13",
        image.I25: "I25",
        image.DATABAR: "DATABAR",
        image.DATABAR_EXP: "DATABAR_EXP",
        image.CODABAR: "CODABAR",
        image.CODE39: "CODE39",
        image.PDF417: "PDF417",
        image.CODE93: "CODE93",
        image.CODE128: "CODE128",
    }
    return barcode_types.get(code.type(), "Unknown barcode")

# Define image detection width and height
DETECT_WIDTH = 640
DETECT_HEIGHT = 480

sensor = None

try:
    # Construct Sensor object using default configuration
    sensor = Sensor(width=DETECT_WIDTH, height=DETECT_HEIGHT)
    # Reset sensor
    sensor.reset()
    # Set output size and format
    sensor.set_framesize(width=DETECT_WIDTH, height=DETECT_HEIGHT)
    sensor.set_pixformat(Sensor.GRAYSCALE)

    # Initialize display
    Display.init(Display.VIRT, width=DETECT_WIDTH, height=DETECT_HEIGHT, fps=100)

    # Initialize media manager
    MediaManager.init()
    # Start sensor
    sensor.run()

    fps = time.clock()

    while True:
        fps.tick()

        # Check whether to exit
        os.exitpoint()
        img = sensor.snapshot()

        # Recognize barcodes in the image
        for code in img.find_barcodes():
            img.draw_rectangle([v for v in code.rect()], color=(255, 0, 0))  # Draw a rectangle around the recognized barcode
            print_args = (
                barcode_name(code),
                code.payload(),
                (180 * code.rotation()) / math.pi,
                code.quality(),
                fps.fps()
            )
            print("Barcode %s, content \"%s\", rotation %f (degrees), quality %d, FPS %f" % print_args)

        # Draw the result onto the screen
        Display.show_image(img)
        gc.collect()

except KeyboardInterrupt:
    print("User stopped")
except BaseException as e:
    print(f"Exception '{e}'")
finally:
    # Stop sensor
    if isinstance(sensor, Sensor):
        sensor.stop()
    # Deinitialize display
    Display.deinit()

    os.exitpoint(os.EXITPOINT_ENABLE_SLEEP)
    time.sleep_ms(100)

    # Release media buffers
    MediaManager.deinit()

Code Explanation#

Module Imports: Import necessary libraries to use the sensor, display, and media management functions.
barcode_name function: Returns the name based on the barcode type, facilitating subsequent processing and display.
Sensor Configuration: Create and configure the sensor object, including setting the output image’s width, height, and format (grayscale image).
Display Initialization: Configure the display output method, which can be HDMI, LCD, or IDE.
Main Loop:
- Capture an image and check the exit condition.
- Recognize barcodes in the image, and draw a red rectangle around them.
- Print the detailed information of the barcode, including type, content, rotation angle, quality, and current frame rate.
Exception Handling: Catch user interrupts or other exceptions to ensure the sensor stops properly and resources are released.

Tip

For the specific interface definition, please refer to find_barcodes.

Barcode Recognition Routine Explanation

Contents

Barcode Recognition Routine Explanation#

Overview#

Example#

Code Explanation#