DM code recognition

Routine Effect Introduction

What is DM code

DM code (Data Matrix code) is a two-dimensional barcode with the following characteristics:

1. The shape is square or rectangular, composed of black and white dots.
2. Supports smaller sizes, suitable for small area marking
3. Strong anti-damage ability, can still be read even if it is damaged by 30%
4. High coding density, can store more data

The difference between DM code and QR code (two-dimensional code)

1. Appearance recognition:

• DM code: only solid border
• QR code: There are 3 positioning points

2. size:

• DM code: can be made very small, suitable for tiny products
• QR code: has a minimum size limit, larger

3. Application scenarios:

• DM code: industrial identification, small parts traceability
• QR code: marketing, payment, website sharing and other popular applications

4. Storage capacity:

• DM code: up to 2335 alphanumeric characters
• QR code: up to 4296 alphanumeric characters

Generate DM code

You can use the DM code generation tool provided in our materials, or you can search for an online DM generator online.

Run the routine

After connecting to the IDE, click the Run button in the lower left corner, and use K230 to aim at the DM code we just generated. You can see that the content of the DM code is recognized on the screen.

The [3.00] in the right bracket refers to the rotation offset angle of the DM code.

It should be noted that the recognition success rate of DM is lower than that of QR Code. If it cannot be recognized, you can try rotating the DM code or the camera.

Code Explanation

The complete example code file for this section is located in [Source Code/06.Codes/04.find_datamatrices]

Key Code

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# 使用默认配置构造 Sensor 对象
# Create a Sensor object with default configuration
sensor = Sensor()
# 重置 sensor
# Reset the sensor
sensor.reset()
​
# 设置输出大小和格式
# Set the output size and pixel format
sensor.set_framesize(width=DETECT_WIDTH, height=DETECT_HEIGHT)
sensor.set_pixformat(Sensor.RGB565)
#    sensor.set_pixformat(Sensor.GRAYSCALE)
​
​
# 初始化显示
# Initialize the display
Display.init(Display.ST7701, width=DETECT_WIDTH, height=DETECT_HEIGHT, to_ide=True)
​
# 初始化媒体管理器
# Initialize the media manager
MediaManager.init()
​
# 启动 sensor
# Start the sensor
sensor.run()
​
fps = time.clock()
​
while True:
    fps.tick()
​
    # 检查是否应该退出
    # Check if we should exit
    if os.exitpoint():
        break
​
        img = sensor.snapshot()
​
        # 遍历图像中的 Data Matrix 条形码
        # Iterate through the Data Matrix codes found in the image
        for matrix in img.find_datamatrices():
            # 绘制识别到的 Data Matrix 码的矩形框
            # Draw the rectangle around the detected Data Matrix code
            (x, y, w, h) = matrix.rect()
            y = y - 25 if y - 25 > 0 else y
            img.draw_rectangle([v for v in matrix.rect()], color=(255, 0, 0), thickness=4)
            # 打印矩阵的行列数、内容、旋转角度（度）以及当前的 FPS
            # Print the matrix's row, column count, payload, rotation in degrees, and current FPS
            print_args = (matrix.payload(), (180 * matrix.rotation()) / math.pi)
            img.draw_string_advanced(x, y, 20, "%s [%.2f]°" % print_args, color=(255,0,0))
​
            print("内容 payload \"%s\", 旋转 rotation %f (度)" % print_args)
​
            # 将结果显示到屏幕上
            # Display the result on the screen
            Display.show_image(img)
​
            # 进行垃圾回收，释放内存
            # Perform garbage collection to release memory
            gc.collect()

Code structure

Execution process:

1. First import the necessary modules and define constants

2. In the try block:

   • Initialize and configure the Sensor

   • Initialize the display and media managers

   • Start Sensor

   • Enter the main loop:

     • Check if you need to exit
     • Get image frame
     • Find Data Matrix Code
     • Plotting and displaying results
     • Performing garbage collection

3. Exception handling:

   • Handling keyboard interrupts
   • Handling other exceptions

4. Finally, in the finally block:

   • Stop Sensor
   • Destroy Display
   • Enable Hibernation Mode
   • Release the media buffer

The detailed flow chart is as follows: