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  • 可能是上手教程里寻球小车代码的bug?



    • # Blob Detection Example
      #
      # This example shows off how to use the find_blobs function to find color
      # blobs in the image. This example in particular looks for dark green objects.
      
      import sensor, image, time
      import car
      from pid import PID
      
      # You may need to tweak the above settings for tracking green things...
      # Select an area in the Framebuffer to copy the color settings.
      
      sensor.reset() # Initialize the camera sensor.
      sensor.set_pixformat(sensor.RGB565) # use RGB565.
      sensor.set_framesize(sensor.QQVGA) # use QQVGA for speed.
      sensor.skip_frames(10) # Let new settings take affect.
      sensor.set_auto_whitebal(False) # turn this off.
      clock = time.clock() # Tracks FPS.
      
      # For color tracking to work really well you should ideally be in a very, very,
      # very, controlled enviroment where the lighting is constant...
      green_threshold   = (76, 96, -110, -30, 8, 66)
      size_threshold = 2000
      x_pid = PID(p=0.5, i=1, imax=100)
      h_pid = PID(p=0.05, i=0.1, imax=50)
      
      def find_max(blobs):
          max_size=0
          for blob in blobs:
              if blob[2]*blob[3] > max_size:
                  max_blob=blob
                  max_size = blob[2]*blob[3]
          return max_blob
      
      while(True):
          clock.tick() # Track elapsed milliseconds between snapshots().
          img = sensor.snapshot() # Take a picture and return the image.
      
          blobs = img.find_blobs([green_threshold])
          if blobs:
              max_blob = find_max(blobs)
              x_error = max_blob[5]-img.width()/2
              h_error = max_blob[2]*max_blob[3]-size_threshold
              print("x error: ", x_error)
              '''
              for b in blobs:
                  # Draw a rect around the blob.
                  img.draw_rectangle(b[0:4]) # rect
                  img.draw_cross(b[5], b[6]) # cx, cy
              '''
              img.draw_rectangle(max_blob[0:4]) # rect
              img.draw_cross(max_blob[5], max_blob[6]) # cx, cy
              x_output=x_pid.get_pid(x_error,1)
              h_output=h_pid.get_pid(h_error,1)
              print("h_output",h_output)
              car.run(-h_output-x_output,-h_output+x_output)
          else:
              car.run(18,-18)
      
      

      上一段代码中的

      def find_max(blobs):
          max_size=0
          for blob in blobs:
              if blob[2]*blob[3] > max_size:
                  max_blob=blob
                  max_size = blob[2]*blob[3]
          return max_blob
      

      需要添加‘’global max_blob''一句 否则在反复接收函数值时会报错
      具体参考https://www.cnblogs.com/zhaijiahui/p/8398480.html



    • def find_max(blobs):
          max_size=0
          max_blob=None
          for blob in blobs:
              if blob[2]*blob[3] > max_size:
                  max_blob=blob
                  max_size = blob[2]*blob[3]
          return max_blob