为什么我的 cv2.imread() 调用返回 None？

Question

I just want to cut the img to samll piece and save it, but somehow cannot save

import os
import cv2
import numpy as np
from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont
import pytesseract


sorted_predict_xy_list = [ [71,180], [221,180], [371,180], [521,180], [671,180], [821,180],
[71,291], [221,291], [371,291], [521,291], [671,291], [821,291],
[71,402], [221,402], [371,402], [521,402], [671,402], [821,402],
[71,513], [221,513], [371,513], [521,513], [671,513], [821,513],
[71,624], [221,624], [371,624], [521,624], [671,624], [821,624] ]

image = cv2.imread("/home/student_DC/desktop/optimization_11_10/original_duplicate.png")
j = 0
while j < len(sorted_predict_xy_list) :
    temp_xy = sorted_predict_xy_list[j]
    x = temp_xy[0]
    y = temp_xy[1]
    small_txt_size_w = 65
    small_txt_size_h = 16
    new_crop = image[y:y+small_txt_size_h, x:x+small_txt_size_w]
    cv2.imwrite("/home/student_DC/desktop/optimization_11_10/output_11_10__001/x_{x}_y_{y}.png", new_crop)
    j+=1

• output:

Traceback (most recent call last):
  File "/home/student_DC/desktop/optimization_11_10/draw_squar_on_duplicate_01N.py", line 26, in <module>
    cv2.imwrite("/home/student_DC/desktop/optimization_11_10/output_11_10__001/x_{x}_y_{y}.png", new_crop)
cv2.error: OpenCV(3.4.15) /tmp/pip-req-build-9opz8s5q/opencv/modules/imgcodecs/src/loadsave.cpp:741: error: (-215:Assertion failed) !_img.empty() in function 'imwrite'

---

by read through discussion Cv2.error: (-215:Assertion failed)._img.empty() in function 'imwrite'
I'm checking my x, y is not empty

import os
import cv2
import numpy as np
from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont
import pytesseract


sorted_predict_xy_list = [ [71,180], [221,180], [371,180], [521,180], [671,180], [821,180],
[71,291], [221,291], [371,291], [521,291], [671,291], [821,291],
[71,402], [221,402], [371,402], [521,402], [671,402], [821,402],
[71,513], [221,513], [371,513], [521,513], [671,513], [821,513],
[71,624], [221,624], [371,624], [521,624], [671,624], [821,624] ]

image = cv2.imread("/home/student_DC/desktop/optimization_11_10/original_duplicate.png")
j = 0
while j < len(sorted_predict_xy_list) :
    temp_xy = sorted_predict_xy_list[j]
    x = temp_xy[0]
    y = temp_xy[1]
    small_txt_size_w = 65
    small_txt_size_h = 16
    new_crop = image[y:y+small_txt_size_h, x:x+small_txt_size_w]
    print("x :" , x  , ",y :",y , ", x+small_txt_size_w", x+small_txt_size_w , ", y+small_txt_size_h :" , y+small_txt_size_h)
    j+=1

• output:

Traceback (most recent call last):
  File "/home/student_DC/desktop/optimization_11_10/draw_squar_on_duplicate_01N.py", line 25, in <module>
    new_crop = image[y:y+small_txt_size_h, x:x+small_txt_size_w]
TypeError: 'NoneType' object is not subscriptable

so far I get here, but don't know how to slove my issue

Answer 1

I did not test.

To solve this error, we must remove the declaration of the new_crop variable and add image.append() on its own line.

image.append(y:y+small_txt_size_h, x:x+small_txt_size_w)
print("x :" , x  , ",y :",y , ", x+small_txt_size_w", x+small_txt_size_w , ", y+small_txt_size_h :" , y+small_txt_size_h)
j+=1

Edit: there is another way instead of append. If this could work.

image = cv2.imread(......    
    f image is None:
        exit
    j = 0