Python / PIL / 画像をグレースケールにする、画像を2値化する

グレースケールにするときは
np.repeat()を使ってAllBrightness = [1,2,3]からAllRGB = [[1,1,1], [2,2,2], [3,3,3]] という排列を作ってImageオブジェクト化すればよい。

2値化するときは、たとえば閾値を100とするなら
AllRGB = [[1,2,3],[10,20,30],[100,200,250]]から[False,False,True]というマスク排列を作ってAllRGB = [[0,0,0],[0,0,0],[255,255,255]]という排列を作ってImageオブジェクト化すればよい。

from PIL import Image

import matplotlib.pyplot as plt
import numpy             as np

class IMAGE:
    def __init__(self, imgPath):
        self.srcImg = Image.open(imgPath)
        self.__initialize()
        
    def __initialize(self):
        self.srcArr        = np.asarray(self.srcImg)
        self.size          = self.srcArr.shape
        self.width         = self.size[1]
        self.height        = self.size[0]
        self.numOfPixels   = self.width * self.height
        self.AllRGB        = self.srcArr.reshape(self.numOfPixels, 3)
        self.AllBrightness = np.mean(self.AllRGB, axis=1, dtype="uint16")
        
    def showImg(self):
        plt.imshow(self.srcImg)
        plt.show()
        return self
        
    def showHist(self):
        plt.figure()
        plt.xlabel("brightness")
        plt.ylabel("freq")
        plt.hist(self.AllBrightness, range=(-0.5, 255.5), bins=256)
        plt.show()
        return self
    
    def changeBrightness(self, shift):
        rgb = self.AllRGB.astype(np.int16) + shift
        rgb = np.clip(rgb, 0, 255)
        rgb = rgb.reshape(self.height, self.width, 3)
        
        self.srcImg = Image.fromarray(rgb.astype(np.uint8))
        self.__initialize()
        return self    
    
    def conv2binary(self, threshold):
        larger  = self.AllBrightness>threshold
        smaller = ~larger
        
        self.AllRGB.flags.writeable = True
        self.AllRGB[larger]  = [255,255,255]
        self.AllRGB[smaller] = [0, 0, 0]
        
        self.AllRGB = self.AllRGB.reshape(self.height, self.width, 3)
        self.srcImg = Image.fromarray(self.AllRGB.astype(np.uint8))
        self.__initialize()
        return self
    
    def conv2gray(self):
        brt = np.repeat(self.AllBrightness, 3)
        brt = brt.reshape(self.height, self.width, 3)

        self.srcImg = Image.fromarray(brt.astype(np.uint8))
        self.__initialize()
        return self
        
    def export(self, filepath):
        self.srcImg.save(filepath)
        return self
    
########
# test #
########
if __name__ == "__main__":
    path = "H:\\img\\nanase6.png"
    
    img = IMAGE(path)
    img.showImg()
    img.showHist()
    
    img.conv2binary(50)
    img.showImg()
    img.showHist()

    img = IMAGE(path)
    img.conv2gray()
    img.showImg()
    img.showHist()