pip install pillow

from PIL import Image


def image_border(src, dst, loc='a', width=3, color=(0, 0, 0)):
    '''
    src: (str) 需要加邊框的圖片路徑
    dst: (str) 加邊框的圖片儲存路徑
    loc: (str) 邊框新增的位置, 預設是'a'(
        四周: 'a' or 'all'
        上: 't' or 'top'
        右: 'r' or 'rigth'
        下: 'b' or 'bottom'
        左: 'l' or 'left'
    )
    width: (int) 邊框寬度 (預設是3)
    color: (int or 3-tuple) 邊框顏色 (預設是0, 表示黑色; 也可以設定為三元組表示RGB顏色)
    '''
 

    # 讀取圖片
    img_ori = Image.open(src)
    w = img_ori.size[0]
    h = img_ori.size[1]

    # 新增邊框
    if loc in ['a', 'all']:
        w += 2*width
        h += 2*width
        img_new = Image.new('RGB', (w, h), color)
        img_new.paste(img_ori, (width, width))
    elif loc in ['t', 'top']:
        h +=
 
 width
        img_new = Image.new('RGB', (w, h), color)
        img_new.paste(img_ori, (0, width, w, h))
    elif loc in ['r', 'right']:
        w += width
        img_new = Image.new('RGB', (w, h), color)
        img_new.paste(img_ori, (0, 0, w-width, h))
    elif loc in ['b', 'bottom']:
        h +=
 
 width
        img_new = Image.new('RGB', (w, h), color)
        img_new.paste(img_ori, (0, 0, w, h-width))
    elif loc in ['l', 'left']:
        w += width
        img_new = Image.new('RGB', (w, h), color)
        img_new.paste(img_ori, (width, 0, w, h))
    else:
        pass

    # 儲存圖片
    img_new.save(dst)


if __name__ == "__main__":
    image_border('old.jpg', 'new.jpg', 'a', 10, color=(255, 0, 0))

https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.new
https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.paste