PIL裁剪和粘贴问题:裁剪不会创建裁剪图像

Question

我正在尝试裁剪图像,然后将裁剪后的图像粘贴到另一个图像的中心.理想情况下,我希望裁剪的图像比粘贴的图像小,以便在粘贴的图像周围有边框,但我不知道是否可能.

这是我尝试过的(以及产生的错误消息):

>>> import Image
>>> grey = Image.new('RGB', (200, 200), "grey")
>>> House = Image.open("House01.jpg")
>>> print grey.size, grey.mode, grey.format
>>>(200, 200) RGB None
>>> print House.size, House.mode, House.format
>>>(300, 300) RGB JPEG
>>> box = (25, 25, 25, 25)
>>> House.crop(box)
>>>Image._ImageCrop image mode=RGB size=0x0 at 0x11AD210>
>>> region = House.crop(box)
>>> region.show()
>>>Traceback (most recent call last):
 >>> File "<pyshell#28>", line 1, in <module>
    region.show()
>>>  File "C:\Python26\lib\site-packages\PIL\Image.py", line 1483, in show
    _show(self, title=title, command=command)
>>>  File "C:\Python26\lib\site-packages\PIL\Image.py", line 2123, in _show
    apply(_showxv, (image,), options)
>>>  File "C:\Python26\lib\site-packages\PIL\Image.py", line 2127, in _showxv
    apply(ImageShow.show, (image, title), options)
>>>  File "C:\Python26\lib\site-packages\PIL\ImageShow.py", line 41, in show
    if viewer.show(image, title=title, **options):
>>>  File "C:\Python26\lib\site-packages\PIL\ImageShow.py", line 66, in show
    self.show_image(image, **options)
>>>  File "C:\Python26\lib\site-packages\PIL\ImageShow.py", line 85, in show_image
    return self.show_file(self.save_image(image), **options)
>>>  File "C:\Python26\lib\site-packages\PIL\ImageShow.py", line 81, in save_image
    return image._dump(format=self.get_format(image))
>>>  File "C:\Python26\lib\site-packages\PIL\Image.py", line 493, in _dump
    self.save(file, format)
>>>  File "C:\Python26\lib\site-packages\PIL\Image.py", line 1439, in save
    save_handler(self, fp, filename)
>>>  File "C:\Python26\lib\site-packages\PIL\BmpImagePlugin.py", line 242, in _save
    ImageFile._save(im, fp, [("raw", (0,0)+im.size, 0, (rawmode, stride, -1))])
>>>  File "C:\Python26\lib\site-packages\PIL\ImageFile.py", line 498, in _save
    e.setimage(im.im, b)
>>>SystemError: tile cannot extend outside image

我可以看到'区域'大小已经制作(0,0),但我不明白为什么.

对此的任何帮助都将非常感谢

Answer 1

裁剪方法的PIL文档说明:

返回当前图像的矩形区域.该框是一个4元组,定义左,上,右和下像素坐标.

这是一个懒惰的操作.对源图像的更改可能会也可能不会反映在裁剪后的图像中.要获取单独的副本,请在裁剪副本上调用load方法.

因此,您应该尝试region = House.crop(box).load()确保获得实际的裁剪副本.

更新:
实际上,如果您使用的是PIL 1.1.6及更高版本,上述内容似乎只能起作用.在之前的版本中,我猜load()不会返回任何内容,因此您无法链接操作.在这种情况下,使用:

region = House.crop(box)
region.load()