调整大小似乎不是简单的方法（液体调整大小在这里不起作用）除了（如第二张图片的问题中所建议的那样）使用 PIL 将图像crop()分成九 (9) 个子图像并分别调整它们的大小（除了角子图像，不会调整大小）。然后使用 PIL 将调整大小的部分粘贴到具有请求的新大小的新图像中paste()。边界仅沿其长度而不是沿其厚度拉伸。如果使用进一步向下提供的resizeExceptBorder()功能调整原始图像的大小，则如下所示：

原始图像 (200 x 30)

new_img_1 = resizeExceptBorder(PIL_image,(300,90),(5,5,5,5))

调整大小的图像 (300 x 90)

new_img_2 = resizeExceptBorder(PIL_image,(400,150),(5,5,5,5))

调整大小 (400 x 150)

这里是我为此目的编写的函数代码：

def resizeExceptBorder(PIL_image, newSize, borderWidths):
    """ 
    newSize = (new_width, new_height)
    borderWidths = (leftWidth, rightWidth, topWidth, bottomWidth)"""
    pl_img = PIL_image
    sXr, sYr = newSize # ( 800, 120 ) # resized size X, Y
    lWx, rWx , tWy, bWy  = borderWidths

    sX,  sY  = pl_img.size
    sXi, sYi = sXr-(lWx+rWx), sYr-(tWy+bWy)

    pl_lft_top = pl_img.crop((     0,     0,    lWx, tWy)) 
    pl_rgt_top = pl_img.crop((sX-rWx,     0,    sX,  tWy))
    pl_lft_btm = pl_img.crop((     0, sY-bWy,   lWx,  sY))
    pl_rgt_btm = pl_img.crop((sX-rWx, sY-bWy,    sX,  sY))
    # ---
    pl_lft_lft = pl_img.crop((     0,    tWy,    lWx,sY-bWy)).resize((lWx ,sYi))
    pl_rgt_rgt = pl_img.crop((sX-rWx,    tWy,     sX,sY-bWy)).resize((rWx ,sYi))
    pl_top_top = pl_img.crop((   lWx,      0, sX-rWx,   tWy)).resize((sXi ,tWy))
    pl_btm_btm = pl_img.crop((   lWx, sY-bWy, sX-rWx,    sY)).resize((sXi ,bWy))
    # ---
    pl_mid_mid = pl_img.crop((   lWx,    tWy, sX-rWx,sY-bWy)).resize((sXi,sYi))
    # -------
    pl_new=Image.new(pl_img.mode, (sXr, sYr)) 
    # ---
    pl_new.paste(pl_mid_mid, (    lWx,    tWy))
    # ---
    pl_new.paste(pl_top_top, (    lWx,      0))
    pl_new.paste(pl_btm_btm, (    lWx,sYr-bWy))
    pl_new.paste(pl_lft_lft, (      0,    tWy))
    pl_new.paste(pl_rgt_rgt, (sXr-rWx,    tWy))
    # ---
    pl_new.paste(pl_lft_top, (      0,     0))
    pl_new.paste(pl_rgt_top, (sXr-rWx,     0))
    pl_new.paste(pl_lft_btm, (      0,sYr-bWy))
    pl_new.paste(pl_rgt_btm, (sXr-rWx,sYr-bWy))
    # ---
    return pl_new
#:def