教學、程式來源:
Binary Thresholding using OpenCV and Python

Adaptive Thresholding - Mean and Gaussian Thresholding using OpenCv and Python

How to Crop and Resize Images [3] | OpenCV Python Tutorials for Beginners 2020

Python 與 OpenCV 裁切圖片教學

bgr 藍、綠、紅 ， 轉成 RGB 紅、綠、藍

openCV 原本是藍、綠、紅 ，所以要轉成一般的 紅、綠、藍

grid_RGB = cv2.cvtColor(img,cv2.COLOR_BGR2RGB) #bgr 藍、綠、紅  轉成 紅、綠、藍

轉成HSV

grid_HSV = cv2.cvtColor(grid_RGB,cv2.COLOR_RGB2HSV) #紅、綠、藍 轉成HSV 

灰階

image_gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

黑白

圖片要先轉灰階再轉黑白，不然怪怪的

ret,white_black = cv2.threshold(image_gray,127,255,cv2.THRESH_BINARY)

圖片改變尺寸

長寬變成1000,1000

width, height = 1000,1000
img = cv2.resize(img,(width,height))
print(img.shape)

圖片選取一部分

# 假設圖片(img)高度是1000，寬度是1000
# 要裁減 左上角 高度100，寬度100。
會是:
imgCropped = img[0:100,0:100]  
代表  imgCropped = img[y的起點:y的終點,x的起點:x的終點]  

不會的

# cv2.ADAPTIVE_THRESH_MEAN_C
more_white_black = cv2.adaptiveThreshold(image_gray,255,cv2.ADAPTIVE_THRESH_MEAN_C,cv2.THRESH_BINARY,57,8)

# cv2.ADAPTIVE_THRESH_GAUSSIAN_C
more_white_black = cv2.adaptiveThreshold(image_gray,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY,63,14)

# cv2.THRESH_BINARY_INV 可以讓黑白顛倒
more_white_black =  cv2.adaptiveThreshold(image_gray,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY_INV,85,15)