Python 3 Pillow 把图像转换成灰度

image2grayscale.py

#!/usr/bin/env python3
import sys
from PIL import Image

# 载入图像
im = Image.open(sys.argv[1])
im.show()

def makeGrayscale(im: 'Image.Image') -> 'Image.Image':
    '''Reads a Pillow image and convert it to grayscale using brightness'''
    # 获取图像长宽
    width, height = im.size

    # 复制一份图像
    dest = im.copy()

    # RGB 到亮度
    def rgb2brightness(r: int, g: int, b: int) -> int:
        '''Converts R, G, B value to brightness'''
        return int(0.3 * r + 0.59 * g + 0.11 * b)

    # 遍历图像的每一个像素
    for i in range(width):
        for j in range(height):
            # 获取 RGB 各通道的值
            # Tuple unpack 的时候最后写 *_ 表示忽略多出来的所有值
            # 有些图像有超过三个通道（比如 PNG），不写的话会报
            # ValueError: too many values to unpack
            r, g, b, *_ = im.getpixel((i, j))
            # 转换当前像素
            brightness = rgb2brightness(r, g, b)
            # 写到目标图片
            dest.putpixel((i, j), (brightness, brightness, brightness))

    return dest

im = makeGrayscale(im)
im.show()