image.crop(box)

# box为元组,其中4个数代表裁切出的矩形四条边的位置
box=(左边x, 上边y, 右边x, 下边y) # x横坐标，y纵坐标
image.crop(box)

图像坐标方向如图：

from PIL import Image
def cut_image(image, count):
    width, height = image.size
    item_width = int(width)
    item_height = int(height/count)
    box_list = []
    # (left, upper, right, lower)
    for i in range(0, count):
        box = (0, i*item_height, item_width, (i+1)*item_height)
        box_list.append(box)
    image_list = [image.crop(box) for box in box_list]
    return image_list
def save_images(image_list):
    index = 1
    for image in image_list:
        image.save('D:/' + str(index) + '.jpg')
        index += 1
def main():
    img = Image.open(r'D:\原.jpg')
    print(img.size)
    image_list = cut_image(img, 5)  # 分割图片
    save_images(image_list)
if __name__ == '__main__':
    main()