高程灰度图tif转png

import cv2
import numpy as np
im = cv2.imread('in.tif',flags=(cv2.IMREAD_GRAYSCALE | cv2.IMREAD_ANYDEPTH))
height = im.shape[0]
width = im.shape[1]
print(height)
print(width)
nmin=4294967296
nmax=0
for row in range(height):
    for col in range(width):
        ntemp=im[row][col]
        if ntemp>nmax:
            nmax=ntemp
        if ntemp<nmin:
            nmin=ntemp
nl=nmax-nmin
print(nmax)
print(nmin)
for row in range(height):
    for col in range(width):
        ntemp=im[row][col]
        im[row][col] = (ntemp - nmin)
cv2.imwrite('out.png', im.astype(np.uint16))
print ('convert complete')