@quy4 sensor.set_windowing(ROI) 这个函数设置的区域最大值好小好小，不能满足需求，

我在find_circles 函数中设置了roi区域，但是上传到电脑上的图像并没有改变，如何改变电脑上的图像区域？

import sensor, image, time, pyb
ROI=(13,0,120,120) 
sensor.reset()
sensor.set_pixformat(sensor.GRAYSCALE) # grayscale is faster
sensor.set_framesize(sensor.QQVGA)
sensor.set_windowing(ROI) 
sensor.skip_frames(time = 2000)
clock = time.clock()
led = pyb.LED(1)

while(True):
    clock.tick()
    led.on()
    img = sensor.snapshot().lens_corr(1.8)
    

    # Circle objects have four values: x, y, r (radius), and magnitude. The
    # magnitude is the strength of the detection of the circle. Higher is
    # better...

    # `threshold` controls how many circles are found. Increase its value
    # to decrease the number of circles detected...

    # `x_margin`, `y_margin`, and `r_margin` control the merging of similar
    # circles in the x, y, and r (radius) directions.

    # r_min, r_max, and r_step control what radiuses of circles are tested.
    # Shrinking the number of tested circle radiuses yields a big performance boost.

    for c in img.find_circles(roi=ROI,threshold = 1200, x_margin = 10, y_margin = 10, r_margin = 10,
            r_min = 1, r_max = 5, r_step = 2):
       #img.draw_circle(c.x(), c.y(), c.r(), color = (255, 0, 0))
       print(c)

   #print("FPS %f" % clock.fps())