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Merge pull request #4630 from radarhere/decoder

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Use _accept function in example plugin
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Hugo van Kemenade 2020-05-17 09:29:13 +03:00 committed by GitHub
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1 changed files with 9 additions and 9 deletions
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18
docs/handbook/writing-your-own-file-decoder.rst
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@ -17,8 +17,8 @@ itself. Such plug-ins usually have names like
Pillow decodes files in 2 stages: Pillow decodes files in 2 stages:
1. It loops over the available image plugins in the loaded order, and 1. It loops over the available image plugins in the loaded order, and
calls the plugin's ``accept`` function with the first 16 bytes of calls the plugin's ``_accept`` function with the first 16 bytes of
the file. If the ``accept`` function returns true, the plugin's the file. If the ``_accept`` function returns true, the plugin's
``_open`` method is called to set up the image metadata and image ``_open`` method is called to set up the image metadata and image
tiles. The ``_open`` method is not for decoding the actual image tiles. The ``_open`` method is not for decoding the actual image
data. data.
@ -53,6 +53,11 @@ true color.
from PIL import Image, ImageFile from PIL import Image, ImageFile
def _accept(prefix):
return prefix[:4] == b"SPAM"
class SpamImageFile(ImageFile.ImageFile): class SpamImageFile(ImageFile.ImageFile):
format = "SPAM" format = "SPAM"
@ -60,12 +65,7 @@ true color.
def _open(self): def _open(self):
# check header header = self.fp.read(128).split()
header = self.fp.read(128)
if header[:4] != b"SPAM":
raise SyntaxError("not a SPAM file")
header = header.split()
# size in pixels (width, height) # size in pixels (width, height)
self._size = int(header[1]), int(header[2]) self._size = int(header[1]), int(header[2])
@ -86,7 +86,7 @@ true color.
("raw", (0, 0) + self.size, 128, (self.mode, 0, 1)) ("raw", (0, 0) + self.size, 128, (self.mode, 0, 1))
] ]
Image.register_open(SpamImageFile.format, SpamImageFile) Image.register_open(SpamImageFile.format, SpamImageFile, _accept)
Image.register_extension(SpamImageFile.format, ".spam") Image.register_extension(SpamImageFile.format, ".spam")
Image.register_extension(SpamImageFile.format, ".spa") # dos version Image.register_extension(SpamImageFile.format, ".spa") # dos version