为什么max_blob没有识别到颜色时显示没有定义，而运行开始时识别到相应颜色就没事？

[ctq3]

# 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
from pyb import UART

sensor.reset() 
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QQVGA) 
sensor.skip_frames(10) 
sensor.set_auto_whitebal(False) 
clock = time.clock() 
uart = UART(3,19200,timeout_char=1000)

green_threshold   = (17, 96, -17, 40, 88, 19)
size_threshold = 2000

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

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)
        img.draw_rectangle(max_blob[0:4]) # rect
        img.draw_cross(max_blob[5], max_blob[6]) # cx, cy
    if max_blob:      #此处max_blob显示没定义
        pan_error = max_blob.cx()-img.width()/2
    if max_blob == None:
        print('旋转')
        uart.write('$ZY!')
        time.sleep_ms(100)

[kidswong999]

在if blobs:上面添加max_blob=None

[ctq3]

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