How to make a binary image with python?

问题

I built my image with cv2.THRESH_BINARY and the function

ret, im_thresh = cv2.threshold( gray_image, 40, 255, cv2.THRESH_BINARY )

BUT White must be 1 to Work with my program.

To help I made:

height = int(np.size(im_thresh, 0))
width = int(np.size(im_thresh, 1))

for x in range(height):
    for y in range(width):
        if im_thresh[x,y]==255:
            im_thresh[x,y] = 1

My question: Have any way to do this faster in python?

回答1:

Try using a boolean index to get and set the values of the arrays, which avoids the nested for loop.

import numpy as np
from numpy import random

# Generating an image of values between 1 and 255. 
im_thresh = random.randint(1,256, (64,64))

# Set anything less than 255 to 0. Unnecessary if cv2 does this during threshold. 
# Must go before the operation below in order not to set all values to 0. 
im_thresh[im_thresh<255] = 0

# Set all values at indices where the array equals 255 to 1.
im_thresh[im_thresh==255] = 1

来源：https://stackoverflow.com/questions/43945749/how-to-make-a-binary-image-with-python