OpenCV 阈值处理

cv2.threshold(src,thresh,maxval,type)

• src = 输入图
• dst = 输出图
• thresh 阈值

maxval 当前像素超过了阈值（或者小于阈值，根据type决定），所赋予的值
type 二值化操作的类型包含以下五种{

· cv2.THRESH_BINARY 超过阈值部分去maxval（最大值，否则取0）
· cv2.THRESH_BINARY_INV (上面的反转)
· cv2.THRESH_TRUNC 大于阈值部分设为阈值，否则不变
· cv2.THRESH_TOZERO 大于阈值部分不变，否则设为0
· cv2.THRESH_TOZERO_INV 上面的反转
}

import cv2
import matplotlib as plt
import numpy as np
'''ret,dst = cv2.threshold(src,thresh,maxval,type)'''
'''
src = 输入图
dst = 输出图
thresh 阈值
maxval 当前像素超过了阈值（或者小于阈值，根据type决定），所赋予的值
type 二值化操作的类型包含以下五种{

·   cv2.THRESH_BINARY   超过阈值部分去maxval（最大值，否则取0）
·   cv2.THRESH_BINARY_INV   (上面的反转)
·   cv2.THRESH_TRUNC        大于阈值部分设为阈值，否则不变
·   cv2.THRESH_TOZERO       大于阈值部分不变，否则设为0
·   cv2.THRESH_TOZERO_INV   上面的反转
}
'''
img = cv2.imread("a28.png")
ret,THRESH_BINARY = cv2.threshold(img,127,255,cv2.THRESH_TOZERO_INV,0)
ret,THRESH_BINARY_INV = cv2.threshold(img,127,255,cv2.THRESH_BINARY_INV,0)
ret,THRESH_TRUNCY = cv2.threshold(img,127,255,cv2.THRESH_TRUNC,0)
ret,THRESH_TOZERO = cv2.threshold(img,127,255,cv2.THRESH_TOZERO,0)
ret,THRESH_TOZERO_INV = cv2.threshold(img,127,255,cv2.THRESH_TOZERO_INV,0)


#或者这样
title = ['THRESH_BINARY','HRESH_BINARY_INV','THRESH_TRUNCY','THRESH_TOZERO','THRESH_TOZERO_INV']
images = [THRESH_BINARY,THRESH_BINARY_INV,THRESH_TRUNCY,THRESH_TOZERO,THRESH_TOZERO_INV]

for i in range(5):
    plt.subplot(3,3,i+1),plt.imshow(images[i],'gray')
    plt.title(title[i])
    plt.xticks([]),plt.yticks([])
plt.show()