python-opencv图片二值化

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简单阈值

像素值高于阈值时，我们给这个像素附一个新值，否则我们给他赋予另外一种颜色，这个函数是cv2.threshhold()。这个函数有两个返回值，第一个为retval，第二个就是处理后的图像这个函数的第一个参数就是原图像，原图像应该是灰度图。第二个参数就是用来对像素值进行分类的阈值。第三个参数就是当像素值高于（有时是小于）阈值时应该被赋予的新的像素值。第四个参数是阈值方法，这些方法包括：

●cv2.THRESH_BINARY

●cv2.THRESH_BINARY_INV

●cv2.THRESH_TRUNC

●cv2.THRESH_TOZERO

●cv2.THRESH_TOZERO_INV

import cv2import numpy as npfrom matplotlib import pyplot as pltimg=cv2.imread('obama.bmp')GrayImage=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)ret,thresh1=cv2.threshold(GrayImage,80,255,cv2.THRESH_BINARY)ret,thresh2=cv2.threshold(GrayImage,80,255,cv2.THRESH_BINARY_INV)ret,thresh3=cv2.threshold(GrayImage,80,255,cv2.THRESH_TRUNC)ret,thresh4=cv2.threshold(GrayImage,80,255,cv2.THRESH_TOZERO)ret,thresh5=cv2.threshold(GrayImage,80,255,cv2.THRESH_TOZERO_INV)titles = ['Gray Image','BINARY','BINARY_INV','TRUNC','TOZERO','TOZERO_INV']images = [GrayImage, thresh1, thresh2, thresh3, thresh4, thresh5]for i in xrange(6):   plt.subplot(2,3,i+1),plt.imshow(images[i],'gray')   plt.title(titles[i])   plt.xticks([]),plt.yticks([])plt.show()

样本图：

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