如何将RGBA字串转换为灰度图像？

from PIL import Image

def rgba_to_grayscale(rgba_string):
    # 解析RGBA字符串
    rgba_values = rgba_string.strip('rgba()').split(',')
    red = int(rgba_values[0])
    green = int(rgba_values[1])
    blue = int(rgba_values[2])
    alpha = float(rgba_values[3])

    # 计算灰度值
    gray = int(0.299 * red + 0.587 * green + 0.114 * blue)

    # 创建灰度图像
    grayscale_image = Image.new('L', (1, 1))

    # 填充灰度值
    grayscale_image.putpixel((0, 0), gray)

    return grayscale_image

# 示例用法
rgba_string = "rgba(100, 150, 200, 1)"
grayscale_image = rgba_to_grayscale(rgba_string)
grayscale_image.show()