请问一下openmv怎么把像素偏移转化成实际距离呢

[vkgq]

#小车上
import sensor, image, time, pyb
from pyb import UART

uart3 = UART(3,115200)#与车
#uart1 = UART(3,115200)

sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QVGA)
#预设大小 窗口宽度 窗口高度sss
#VGA 640 480
#QVGA 320 240
#QQVGA 160 120
#视觉中心点：（160，120）
sensor.skip_frames(time = 2000)
sensor.set_auto_gain(False) # 在进行颜色追踪时，必须关闭
sensor.set_auto_whitebal(False) # 在进行颜色追踪时，必须关闭
clock = time.clock()

#a=2
#a=''
#o0=''
#o1=''
#o2=''
#o3=''
#o4=''

#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

def find_max(blobs):
max_size=0
for blob in blobs:
if blob.pixels() > max_size:
max_blob = blob
max_size = blob.pixels()
return max_blob

while(True):
clock.tick()
img = sensor.snapshot()
#找蓝色(24, 80, -48, 60, -75, -20)(0, 47, -20, 27, -78, -6)

blobs = img.find_blobs([(24, 80, -48, 60, -75, -20)],area_threshold=3,pixels_threshold=3)

blobs = img.find_blobs([(70, 100, -10, 10,-10, 10)], area_threshold=3, pixels_threshold=3)
#blobs = img.find_blobs([(24, 70, 17, 127, -10, 127)],area_threshold=3,pixels_threshold=3)
#max_blob = find_max(blobs)
if blobs:
    max_blob = find_max(blobs)
    #c = max_blob[0]
    x=max_blob[5]-160
    y=max_blob[6]-120
    img.draw_cross(max_blob[5], max_blob[6],(0,0,255)) # 在物体的中心点(cx,xy)画一个十字
    x_L8 = int(x) & 0x00FF #取低八位
    x_H8 = (int(x)>>8) & 0x00FF #取高八位
    y_L8 = int(y) & 0x00FF #取低八位
    y_H8 = (int(y)>>8) & 0x00FF #取高八位
    data1 = bytearray([1,x_L8,x_H8,y_L8,y_H8,0x0A])
    print("(%d,%d)" %(x,y))
    uart3.write(data1)
else:
    print("no")
    data1 = bytearray([9,0x0A])
    uart3.write(data1)