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324 lines
10 KiB
Python
324 lines
10 KiB
Python
#
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# The Python Imaging Library.
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# $Id$
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#
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# PPM support for PIL
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#
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# History:
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# 96-03-24 fl Created
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# 98-03-06 fl Write RGBA images (as RGB, that is)
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#
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# Copyright (c) Secret Labs AB 1997-98.
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# Copyright (c) Fredrik Lundh 1996.
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#
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# See the README file for information on usage and redistribution.
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#
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from . import Image, ImageFile
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#
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# --------------------------------------------------------------------
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b_whitespace = b"\x20\x09\x0a\x0b\x0c\x0d"
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MODES = {
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# standard
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b"P1": "1",
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b"P2": "L",
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b"P3": "RGB",
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b"P4": "1",
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b"P5": "L",
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b"P6": "RGB",
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# extensions
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b"P0CMYK": "CMYK",
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# PIL extensions (for test purposes only)
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b"PyP": "P",
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b"PyRGBA": "RGBA",
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b"PyCMYK": "CMYK",
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}
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def _accept(prefix):
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return prefix[0:1] == b"P" and prefix[1] in b"0123456y"
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##
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# Image plugin for PBM, PGM, and PPM images.
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class PpmImageFile(ImageFile.ImageFile):
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format = "PPM"
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format_description = "Pbmplus image"
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def _read_magic(self):
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magic = b""
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# read until whitespace or longest available magic number
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for _ in range(6):
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c = self.fp.read(1)
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if not c or c in b_whitespace:
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break
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magic += c
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return magic
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def _read_token(self):
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token = b""
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while len(token) <= 10: # read until next whitespace or limit of 10 characters
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c = self.fp.read(1)
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if not c:
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break
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elif c in b_whitespace: # token ended
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if not token:
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# skip whitespace at start
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continue
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break
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elif c == b"#":
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# ignores rest of the line; stops at CR, LF or EOF
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while self.fp.read(1) not in b"\r\n":
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pass
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continue
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token += c
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if not token:
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# Token was not even 1 byte
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raise ValueError("Reached EOF while reading header")
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elif len(token) > 10:
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raise ValueError(f"Token too long in file header: {token}")
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return token
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def _open(self):
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magic_number = self._read_magic()
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try:
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mode = MODES[magic_number]
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except KeyError:
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raise SyntaxError("not a PPM file")
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if magic_number in (b"P1", b"P4"):
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self.custom_mimetype = "image/x-portable-bitmap"
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elif magic_number in (b"P2", b"P5"):
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self.custom_mimetype = "image/x-portable-graymap"
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elif magic_number in (b"P3", b"P6"):
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self.custom_mimetype = "image/x-portable-pixmap"
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for ix in range(3):
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token = int(self._read_token())
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if ix == 0: # token is the x size
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xsize = token
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elif ix == 1: # token is the y size
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ysize = token
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if mode == "1":
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self.mode = "1"
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rawmode = "1;I"
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break
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else:
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self.mode = rawmode = mode
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elif ix == 2: # token is maxval
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maxval = token
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if maxval > 255:
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if not mode == "L":
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raise ValueError(f"Too many colors for band: {maxval}")
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if maxval < 2**16:
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self.mode = "I"
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rawmode = "I;16B"
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else:
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self.mode = "I"
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rawmode = "I;32B"
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decoder_name = "raw"
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if magic_number in (b"P1", b"P2", b"P3"):
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decoder_name = "ppm_plain"
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self._size = xsize, ysize
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self.tile = [
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(decoder_name, (0, 0, xsize, ysize), self.fp.tell(), (rawmode, 0, 1))
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]
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#
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# --------------------------------------------------------------------
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class PpmPlainDecoder(ImageFile.PyDecoder):
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_pulls_fd = True
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def _read_block(self):
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return self.fd.read(10**6)
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def _find_comment_end(self, block, start=0):
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a = block.find(b"\n", start)
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b = block.find(b"\r", start)
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return min(a, b) if a * b > 0 else max(a, b) # lowest nonnegative index (or -1)
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def _ignore_comments(self, block):
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"""
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Deletes comments from block.
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If comment does not end in this block, raises a flag.
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"""
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comment_spans = False
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while True:
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comment_start = block.find(b"#") # look for next comment
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if comment_start == -1: # no comment found
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break
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comment_end = self._find_comment_end(block, comment_start)
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if comment_end != -1: # comment ends in this block
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# delete comment
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block = block[:comment_start] + block[comment_end + 1 :]
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else: # last comment continues to next block(s)
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block = block[:comment_start]
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comment_spans = True
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break
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return block, comment_spans
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def _decode_bitonal(self):
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"""
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This is a separate method because the plain PBM format all data tokens
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are exactly one byte, and so the inter-token whitespace is optional.
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"""
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decoded_data = bytearray()
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total_bytes = self.state.xsize * self.state.ysize
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comment_spans = False
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while len(decoded_data) != total_bytes:
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block = self._read_block() # read next block
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if not block:
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# eof
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break
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while block and comment_spans:
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comment_end = self._find_comment_end(block)
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if comment_end != -1: # comment ends in this block
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comment_spans = False
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block = block[comment_end + 1 :] # delete tail of previous comment
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else: # comment spans whole block
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block = self._read_block()
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block, comment_spans = self._ignore_comments(block)
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tokens = b"".join(block.split())
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for token in tokens:
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if token not in (48, 49):
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raise ValueError(f"Invalid token for this mode: {bytes([token])}")
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decoded_data = (decoded_data + tokens)[:total_bytes]
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invert = bytes.maketrans(b"01", b"\xFF\x00")
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return decoded_data.translate(invert)
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def _decode_blocks(self, channels=1, depth=8):
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decoded_data = bytearray()
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# HACK: 32-bit grayscale uses signed int
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maxval = 2 ** (31 if depth == 32 else depth) - 1
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max_len = 10
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bytes_per_sample = depth // 8
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total_bytes = self.state.xsize * self.state.ysize * channels * bytes_per_sample
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comment_spans = False
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half_token = False
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while len(decoded_data) != total_bytes:
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block = self._read_block() # read next block
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if not block:
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if half_token:
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block = bytearray(b" ") # flush half_token
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else:
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# eof
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break
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while block and comment_spans:
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comment_end = self._find_comment_end(block)
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if comment_end != -1: # comment ends in this block
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block = block[comment_end + 1 :] # delete tail of previous comment
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break
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else: # comment spans whole block
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block = self._read_block()
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block, comment_spans = self._ignore_comments(block)
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if half_token:
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block = half_token + block # stitch half_token to new block
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tokens = block.split()
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if block and not block[-1:].isspace(): # block might split token
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half_token = tokens.pop() # save half token for later
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if len(half_token) > max_len: # prevent buildup of half_token
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raise ValueError(
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f"Token too long found in data: {half_token[:max_len + 1]}"
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)
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for token in tokens:
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if len(token) > max_len:
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raise ValueError(
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f"Token too long found in data: {token[:max_len + 1]}"
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)
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token = int(token)
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if token > maxval:
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raise ValueError(f"Channel value too large for this mode: {token}")
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decoded_data += token.to_bytes(bytes_per_sample, "big")
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if len(decoded_data) == total_bytes: # finished!
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break
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return decoded_data
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def decode(self, buffer):
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rawmode = self.args[0]
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if self.mode == "1":
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decoded_data = self._decode_bitonal()
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rawmode = "1;8"
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elif self.mode == "L":
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decoded_data = self._decode_blocks(channels=1, depth=8)
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elif self.mode == "I":
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if rawmode == "I;16B":
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decoded_data = self._decode_blocks(channels=1, depth=16)
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elif rawmode == "I;32B":
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decoded_data = self._decode_blocks(channels=1, depth=32)
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elif self.mode == "RGB":
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decoded_data = self._decode_blocks(channels=3, depth=8)
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self.set_as_raw(bytes(decoded_data), rawmode)
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return -1, 0
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#
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# --------------------------------------------------------------------
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def _save(im, fp, filename):
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if im.mode == "1":
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rawmode, head = "1;I", b"P4"
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elif im.mode == "L":
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rawmode, head = "L", b"P5"
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elif im.mode == "I":
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if im.getextrema()[1] < 2**16:
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rawmode, head = "I;16B", b"P5"
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else:
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rawmode, head = "I;32B", b"P5"
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elif im.mode == "RGB":
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rawmode, head = "RGB", b"P6"
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elif im.mode == "RGBA":
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rawmode, head = "RGB", b"P6"
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else:
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raise OSError(f"cannot write mode {im.mode} as PPM")
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fp.write(head + ("\n%d %d\n" % im.size).encode("ascii"))
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if head == b"P6":
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fp.write(b"255\n")
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if head == b"P5":
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if rawmode == "L":
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fp.write(b"255\n")
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elif rawmode == "I;16B":
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fp.write(b"65535\n")
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elif rawmode == "I;32B":
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fp.write(b"2147483648\n")
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ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, 0, 1))])
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# ALTERNATIVE: save via builtin debug function
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# im._dump(filename)
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#
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# --------------------------------------------------------------------
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Image.register_decoder("ppm_plain", PpmPlainDecoder)
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Image.register_open(PpmImageFile.format, PpmImageFile, _accept)
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Image.register_save(PpmImageFile.format, _save)
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Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm"])
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Image.register_mime(PpmImageFile.format, "image/x-portable-anymap")
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