PIL getbbox方法如何工作？

I'm trying to understand the PIL getbbox (get boundary box) function, which "Calculates the bounding box of the non-zero regions in the image."

我正在尝试理解PIL getbbox(获取边界框)功能,即“计算图像中非零区域的边界框”。

In the following code, I use getbbox and it returns exactly what I expect it to with simple grayscale images.

在下面的代码中,我使用了getbbox,它使用简单的灰度图像返回了我期望的结果。

import numpy as np
from PIL import Image, ImageFont, ImageDraw, ImageEnhance,ImageChops
import PIL

def trim(im):
dr = ImageDraw.Draw(im)
bg = Image.new(im.mode, im.size, im.getpixel((0,0)))

diff = ImageChops.difference(im, bg)
bbox = diff.getbbox() 

#None if getbbox returns None
if bbox:
     return im.crop(bbox)

I don't however understand how it works accord to its source code. Besides the self.load(), it seems to do some sort of recursive call on itself. I thought recursive functions needed terminating conditions, but I see none?

但是,根据其源代码,我不了解它是如何工作的。除了self.load()之外,它似乎还在进行某种递归调用。我认为递归函数需要终止条件,但我没有看到?

I feel like it has something to do with somehow removing the black pixels in the image array, but I just don't understand these seemingly cryptic 2 lines of code (below). Any help in me understanding this would be appreciated.

我觉得它与以某种方式删除图像阵列中的黑色像素有关,但我只是不明白这些看似神秘的2行代码(下图)。任何帮助我理解这一点将不胜感激。

def getbbox(self):
    """
    Calculates the bounding box of the non-zero regions in the
    image.
    :returns: The bounding box is returned as a 4-tuple defining the
       left, upper, right, and lower pixel coordinate. If the image
       is completely empty, this method returns None.
    """

    self.load()
    return self.im.getbbox()

edit: pasted in source code

编辑:粘贴在源代码中

1 个解决方案

#1

As has been commented, this is not recursion. im.getbbox() calls https://github.com/python-pillow/Pillow/blob/master/src/_imaging.c#L1947

正如已经评论过的,这不是递归。 im.getbbox()调用https://github.com/python-pillow/Pillow/blob/master/src/_imaging.c#L1947

That then calls ImagingGetBBox - https://github.com/python-pillow/Pillow/blob/master/src/libImaging/GetBBox.c#L24

然后调用ImagingGetBBox - https://github.com/python-pillow/Pillow/blob/master/src/libImaging/GetBBox.c#L24

#1