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778 lines
25 KiB
Python
778 lines
25 KiB
Python
#
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# The Python Imaging Library.
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# $Id$
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#
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# GIF file handling
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#
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# History:
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# 1995-09-01 fl Created
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# 1996-12-14 fl Added interlace support
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# 1996-12-30 fl Added animation support
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# 1997-01-05 fl Added write support, fixed local colour map bug
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# 1997-02-23 fl Make sure to load raster data in getdata()
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# 1997-07-05 fl Support external decoder (0.4)
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# 1998-07-09 fl Handle all modes when saving (0.5)
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# 1998-07-15 fl Renamed offset attribute to avoid name clash
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# 2001-04-16 fl Added rewind support (seek to frame 0) (0.6)
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# 2001-04-17 fl Added palette optimization (0.7)
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# 2002-06-06 fl Added transparency support for save (0.8)
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# 2004-02-24 fl Disable interlacing for small images
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#
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# Copyright (c) 1997-2004 by Secret Labs AB
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# Copyright (c) 1995-2004 by Fredrik Lundh
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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 PIL import Image, ImageFile, ImagePalette, \
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ImageChops, ImageSequence, _binary
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__version__ = "0.9"
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# --------------------------------------------------------------------
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# Helpers
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i8 = _binary.i8
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i16 = _binary.i16le
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o8 = _binary.o8
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o16 = _binary.o16le
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# --------------------------------------------------------------------
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# Identify/read GIF files
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def _accept(prefix):
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return prefix[:6] in [b"GIF87a", b"GIF89a"]
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##
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# Image plugin for GIF images. This plugin supports both GIF87 and
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# GIF89 images.
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class GifImageFile(ImageFile.ImageFile):
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format = "GIF"
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format_description = "Compuserve GIF"
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global_palette = None
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def data(self):
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s = self.fp.read(1)
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if s and i8(s):
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return self.fp.read(i8(s))
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return None
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def _open(self):
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# Screen
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s = self.fp.read(13)
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if s[:6] not in [b"GIF87a", b"GIF89a"]:
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raise SyntaxError("not a GIF file")
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self.info["version"] = s[:6]
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self.size = i16(s[6:]), i16(s[8:])
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self.tile = []
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flags = i8(s[10])
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bits = (flags & 7) + 1
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if flags & 128:
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# get global palette
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self.info["background"] = i8(s[11])
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# check if palette contains colour indices
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p = self.fp.read(3 << bits)
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for i in range(0, len(p), 3):
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if not (i//3 == i8(p[i]) == i8(p[i+1]) == i8(p[i+2])):
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p = ImagePalette.raw("RGB", p)
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self.global_palette = self.palette = p
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break
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self.__fp = self.fp # FIXME: hack
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self.__rewind = self.fp.tell()
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self._n_frames = None
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self._is_animated = None
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self._seek(0) # get ready to read first frame
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@property
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def n_frames(self):
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if self._n_frames is None:
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current = self.tell()
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try:
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while True:
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self.seek(self.tell() + 1)
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except EOFError:
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self._n_frames = self.tell() + 1
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self.seek(current)
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return self._n_frames
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@property
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def is_animated(self):
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if self._is_animated is None:
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current = self.tell()
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try:
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self.seek(1)
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self._is_animated = True
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except EOFError:
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self._is_animated = False
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self.seek(current)
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return self._is_animated
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def seek(self, frame):
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if frame == self.__frame:
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return
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if frame < self.__frame:
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self._seek(0)
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last_frame = self.__frame
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for f in range(self.__frame + 1, frame + 1):
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try:
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self._seek(f)
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except EOFError:
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self.seek(last_frame)
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raise EOFError("no more images in GIF file")
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def _seek(self, frame):
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if frame == 0:
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# rewind
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self.__offset = 0
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self.dispose = None
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self.dispose_extent = [0, 0, 0, 0] # x0, y0, x1, y1
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self.__frame = -1
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self.__fp.seek(self.__rewind)
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self._prev_im = None
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self.disposal_method = 0
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else:
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# ensure that the previous frame was loaded
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if not self.im:
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self.load()
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if frame != self.__frame + 1:
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raise ValueError("cannot seek to frame %d" % frame)
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self.__frame = frame
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self.tile = []
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self.fp = self.__fp
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if self.__offset:
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# backup to last frame
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self.fp.seek(self.__offset)
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while self.data():
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pass
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self.__offset = 0
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if self.dispose:
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self.im.paste(self.dispose, self.dispose_extent)
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from copy import copy
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self.palette = copy(self.global_palette)
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while True:
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s = self.fp.read(1)
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if not s or s == b";":
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break
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elif s == b"!":
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#
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# extensions
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#
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s = self.fp.read(1)
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block = self.data()
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if i8(s) == 249:
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#
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# graphic control extension
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#
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flags = i8(block[0])
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if flags & 1:
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self.info["transparency"] = i8(block[3])
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self.info["duration"] = i16(block[1:3]) * 10
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# disposal method - find the value of bits 4 - 6
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dispose_bits = 0b00011100 & flags
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dispose_bits = dispose_bits >> 2
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if dispose_bits:
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# only set the dispose if it is not
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# unspecified. I'm not sure if this is
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# correct, but it seems to prevent the last
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# frame from looking odd for some animations
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self.disposal_method = dispose_bits
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elif i8(s) == 254:
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#
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# comment extension
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#
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self.info["comment"] = block
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elif i8(s) == 255:
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#
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# application extension
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#
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self.info["extension"] = block, self.fp.tell()
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if block[:11] == b"NETSCAPE2.0":
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block = self.data()
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if len(block) >= 3 and i8(block[0]) == 1:
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self.info["loop"] = i16(block[1:3])
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while self.data():
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pass
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elif s == b",":
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#
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# local image
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#
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s = self.fp.read(9)
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# extent
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x0, y0 = i16(s[0:]), i16(s[2:])
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x1, y1 = x0 + i16(s[4:]), y0 + i16(s[6:])
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self.dispose_extent = x0, y0, x1, y1
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flags = i8(s[8])
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interlace = (flags & 64) != 0
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if flags & 128:
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bits = (flags & 7) + 1
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self.palette =\
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ImagePalette.raw("RGB", self.fp.read(3 << bits))
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# image data
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bits = i8(self.fp.read(1))
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self.__offset = self.fp.tell()
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self.tile = [("gif",
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(x0, y0, x1, y1),
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self.__offset,
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(bits, interlace))]
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break
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else:
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pass
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# raise IOError, "illegal GIF tag `%x`" % i8(s)
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try:
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if self.disposal_method < 2:
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# do not dispose or none specified
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self.dispose = None
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elif self.disposal_method == 2:
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# replace with background colour
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self.dispose = Image.core.fill("P", self.size,
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self.info["background"])
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else:
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# replace with previous contents
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if self.im:
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self.dispose = self.im.copy()
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# only dispose the extent in this frame
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if self.dispose:
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self.dispose = self.dispose.crop(self.dispose_extent)
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except (AttributeError, KeyError):
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pass
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if not self.tile:
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# self.__fp = None
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raise EOFError
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self.mode = "L"
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if self.palette:
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self.mode = "P"
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def tell(self):
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return self.__frame
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def load_end(self):
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ImageFile.ImageFile.load_end(self)
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# if the disposal method is 'do not dispose', transparent
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# pixels should show the content of the previous frame
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if self._prev_im and self.disposal_method == 1:
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# we do this by pasting the updated area onto the previous
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# frame which we then use as the current image content
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updated = self.im.crop(self.dispose_extent)
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self._prev_im.paste(updated, self.dispose_extent,
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updated.convert('RGBA'))
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self.im = self._prev_im
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self._prev_im = self.im.copy()
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# --------------------------------------------------------------------
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# Write GIF files
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try:
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import _imaging_gif
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except ImportError:
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_imaging_gif = None
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RAWMODE = {
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"1": "L",
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"L": "L",
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"P": "P",
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}
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def _convert_mode(im, initial_call=False):
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# convert on the fly (EXPERIMENTAL -- I'm not sure PIL
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# should automatically convert images on save...)
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if Image.getmodebase(im.mode) == "RGB":
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if initial_call:
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palette_size = 256
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if im.palette:
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palette_size = len(im.palette.getdata()[1]) // 3
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return im.convert("P", palette=1, colors=palette_size)
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else:
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return im.convert("P")
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return im.convert("L")
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def _save_all(im, fp, filename):
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_save(im, fp, filename, save_all=True)
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def _save(im, fp, filename, save_all=False):
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im.encoderinfo.update(im.info)
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if _imaging_gif:
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# call external driver
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try:
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_imaging_gif.save(im, fp, filename)
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return
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except IOError:
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pass # write uncompressed file
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if im.mode in RAWMODE:
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im_out = im.copy()
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else:
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im_out = _convert_mode(im, True)
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# header
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try:
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palette = im.encoderinfo["palette"]
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except KeyError:
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palette = None
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im.encoderinfo["optimize"] = im.encoderinfo.get("optimize", True)
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if save_all:
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previous = None
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first_frame = None
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append_images = im.encoderinfo.get("append_images", [])
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for imSequence in [im]+append_images:
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for im_frame in ImageSequence.Iterator(imSequence):
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encoderinfo = im.encoderinfo.copy()
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im_frame = _convert_mode(im_frame)
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# To specify duration, add the time in milliseconds to getdata(),
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# e.g. getdata(im_frame, duration=1000)
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if not previous:
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# global header
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first_frame = getheader(im_frame, palette, encoderinfo)[0]
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first_frame += getdata(im_frame, (0, 0), **encoderinfo)
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else:
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if first_frame:
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for s in first_frame:
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fp.write(s)
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first_frame = None
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# delta frame
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delta = ImageChops.subtract_modulo(im_frame, previous.copy())
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bbox = delta.getbbox()
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if bbox:
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# compress difference
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encoderinfo['include_color_table'] = True
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for s in getdata(im_frame.crop(bbox),
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bbox[:2], **encoderinfo):
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fp.write(s)
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else:
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# FIXME: what should we do in this case?
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pass
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previous = im_frame
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if first_frame:
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save_all = False
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if not save_all:
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header = getheader(im_out, palette, im.encoderinfo)[0]
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for s in header:
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fp.write(s)
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flags = 0
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if get_interlace(im):
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flags = flags | 64
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# local image header
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_get_local_header(fp, im, (0, 0), flags)
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im_out.encoderconfig = (8, get_interlace(im))
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ImageFile._save(im_out, fp, [("gif", (0, 0)+im.size, 0,
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RAWMODE[im_out.mode])])
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fp.write(b"\0") # end of image data
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fp.write(b";") # end of file
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if hasattr(fp, "flush"):
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fp.flush()
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def get_interlace(im):
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try:
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interlace = im.encoderinfo["interlace"]
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except KeyError:
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interlace = 1
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# workaround for @PIL153
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if min(im.size) < 16:
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interlace = 0
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return interlace
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def _get_local_header(fp, im, offset, flags):
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transparent_color_exists = False
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try:
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transparency = im.encoderinfo["transparency"]
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except KeyError:
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pass
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else:
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transparency = int(transparency)
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# optimize the block away if transparent color is not used
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transparent_color_exists = True
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if _get_optimize(im, im.encoderinfo):
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used_palette_colors = _get_used_palette_colors(im)
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# adjust the transparency index after optimize
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if len(used_palette_colors) < 256:
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for i in range(len(used_palette_colors)):
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if used_palette_colors[i] == transparency:
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transparency = i
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transparent_color_exists = True
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break
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else:
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transparent_color_exists = False
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if "duration" in im.encoderinfo:
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duration = int(im.encoderinfo["duration"] / 10)
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else:
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duration = 0
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if transparent_color_exists or duration != 0:
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transparency_flag = 1 if transparent_color_exists else 0
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if not transparent_color_exists:
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transparency = 0
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fp.write(b"!" +
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o8(249) + # extension intro
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o8(4) + # length
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o8(transparency_flag) + # packed fields
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o16(duration) + # duration
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o8(transparency) + # transparency index
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o8(0))
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if "comment" in im.encoderinfo and 1 <= len(im.encoderinfo["comment"]) <= 255:
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fp.write(b"!" +
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o8(254) + # extension intro
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o8(len(im.encoderinfo["comment"])) +
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im.encoderinfo["comment"] +
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o8(0))
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if "loop" in im.encoderinfo:
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number_of_loops = im.encoderinfo["loop"]
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fp.write(b"!" +
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o8(255) + # extension intro
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o8(11) +
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b"NETSCAPE2.0" +
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o8(3) +
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o8(1) +
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o16(number_of_loops) + # number of loops
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o8(0))
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include_color_table = im.encoderinfo.get('include_color_table')
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if include_color_table:
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try:
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palette = im.encoderinfo["palette"]
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except KeyError:
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palette = None
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palette_bytes = _get_palette_bytes(im, palette, im.encoderinfo)[0]
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color_table_size = _get_color_table_size(palette_bytes)
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if color_table_size:
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flags = flags | 128 # local color table flag
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flags = flags | color_table_size
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fp.write(b"," +
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o16(offset[0]) + # offset
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o16(offset[1]) +
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o16(im.size[0]) + # size
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o16(im.size[1]) +
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o8(flags)) # flags
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if include_color_table and color_table_size:
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fp.write(_get_header_palette(palette_bytes))
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fp.write(o8(8)) # bits
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def _save_netpbm(im, fp, filename):
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#
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# If you need real GIF compression and/or RGB quantization, you
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# can use the external NETPBM/PBMPLUS utilities. See comments
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# below for information on how to enable this.
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import os
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from subprocess import Popen, check_call, PIPE, CalledProcessError
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import tempfile
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file = im._dump()
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if im.mode != "RGB":
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with open(filename, 'wb') as f:
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stderr = tempfile.TemporaryFile()
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check_call(["ppmtogif", file], stdout=f, stderr=stderr)
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else:
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with open(filename, 'wb') as f:
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# Pipe ppmquant output into ppmtogif
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# "ppmquant 256 %s | ppmtogif > %s" % (file, filename)
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quant_cmd = ["ppmquant", "256", file]
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togif_cmd = ["ppmtogif"]
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stderr = tempfile.TemporaryFile()
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quant_proc = Popen(quant_cmd, stdout=PIPE, stderr=stderr)
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stderr = tempfile.TemporaryFile()
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togif_proc = Popen(togif_cmd, stdin=quant_proc.stdout, stdout=f,
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stderr=stderr)
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# Allow ppmquant to receive SIGPIPE if ppmtogif exits
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quant_proc.stdout.close()
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retcode = quant_proc.wait()
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if retcode:
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raise CalledProcessError(retcode, quant_cmd)
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retcode = togif_proc.wait()
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if retcode:
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raise CalledProcessError(retcode, togif_cmd)
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try:
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os.unlink(file)
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except OSError:
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pass
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# --------------------------------------------------------------------
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# GIF utilities
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def _get_optimize(im, info):
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return im.mode in ("P", "L") and info and info.get("optimize", 0)
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def _get_used_palette_colors(im):
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used_palette_colors = []
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# check which colors are used
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i = 0
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for count in im.histogram():
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if count:
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used_palette_colors.append(i)
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i += 1
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return used_palette_colors
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def _get_color_table_size(palette_bytes):
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# calculate the palette size for the header
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import math
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color_table_size = int(math.ceil(math.log(len(palette_bytes)//3, 2)))-1
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if color_table_size < 0:
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color_table_size = 0
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return color_table_size
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def _get_header_palette(palette_bytes):
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color_table_size = _get_color_table_size(palette_bytes)
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# add the missing amount of bytes
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# the palette has to be 2<<n in size
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actual_target_size_diff = (2 << color_table_size) - len(palette_bytes)//3
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if actual_target_size_diff > 0:
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palette_bytes += o8(0) * 3 * actual_target_size_diff
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return palette_bytes
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# Force optimization so that we can test performance against
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# cases where it took lots of memory and time previously.
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_FORCE_OPTIMIZE = False
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def _get_palette_bytes(im, palette, info):
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if im.mode == "P":
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if palette and isinstance(palette, bytes):
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source_palette = palette[:768]
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else:
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source_palette = im.im.getpalette("RGB")[:768]
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else: # L-mode
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if palette and isinstance(palette, bytes):
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source_palette = palette[:768]
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else:
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source_palette = bytearray(i//3 for i in range(768))
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used_palette_colors = palette_bytes = None
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if _get_optimize(im, info):
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used_palette_colors = _get_used_palette_colors(im)
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# Potentially expensive operation.
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# The palette saves 3 bytes per color not used, but palette
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# lengths are restricted to 3*(2**N) bytes. Max saving would
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# be 768 -> 6 bytes if we went all the way down to 2 colors.
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# * If we're over 128 colors, we can't save any space.
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# * If there aren't any holes, it's not worth collapsing.
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# * If we have a 'large' image, the palette is in the noise.
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# create the new palette if not every color is used
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if _FORCE_OPTIMIZE or im.mode == 'L' or \
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(len(used_palette_colors) <= 128 and
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max(used_palette_colors) > len(used_palette_colors) and
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im.width * im.height < 512 * 512):
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palette_bytes = b""
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new_positions = [0]*256
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# pick only the used colors from the palette
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for i, oldPosition in enumerate(used_palette_colors):
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palette_bytes += source_palette[oldPosition*3:oldPosition*3+3]
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new_positions[oldPosition] = i
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# replace the palette color id of all pixel with the new id
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# Palette images are [0..255], mapped through a 1 or 3
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# byte/color map. We need to remap the whole image
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# from palette 1 to palette 2. New_positions is
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# an array of indexes into palette 1. Palette 2 is
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# palette 1 with any holes removed.
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# We're going to leverage the convert mechanism to use the
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# C code to remap the image from palette 1 to palette 2,
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# by forcing the source image into 'L' mode and adding a
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# mapping 'L' mode palette, then converting back to 'L'
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# sans palette thus converting the image bytes, then
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# assigning the optimized RGB palette.
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# perf reference, 9500x4000 gif, w/~135 colors
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# 14 sec prepatch, 1 sec postpatch with optimization forced.
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mapping_palette = bytearray(new_positions)
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m_im = im.copy()
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m_im.mode = 'P'
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m_im.palette = ImagePalette.ImagePalette("RGB",
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palette=mapping_palette*3,
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size=768)
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#possibly set palette dirty, then
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#m_im.putpalette(mapping_palette, 'L') # converts to 'P'
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# or just force it.
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# UNDONE -- this is part of the general issue with palettes
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m_im.im.putpalette(*m_im.palette.getdata())
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m_im = m_im.convert('L')
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# Internally, we require 768 bytes for a palette.
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new_palette_bytes = (palette_bytes +
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(768 - len(palette_bytes)) * b'\x00')
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m_im.putpalette(new_palette_bytes)
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m_im.palette = ImagePalette.ImagePalette("RGB",
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palette=palette_bytes,
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size=len(palette_bytes))
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# oh gawd, this is modifying the image in place so I can pass by ref.
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# REFACTOR SOONEST
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im.frombytes(m_im.tobytes())
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if not palette_bytes:
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palette_bytes = source_palette
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# returning palette, _not_ padded to 768 bytes like our internal ones.
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return palette_bytes, used_palette_colors
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def getheader(im, palette=None, info=None):
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"""Return a list of strings representing a GIF header"""
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# Header Block
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# http://www.matthewflickinger.com/lab/whatsinagif/bits_and_bytes.asp
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version = b"87a"
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for extensionKey in ["transparency", "duration", "loop", "comment"]:
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if info and extensionKey in info:
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if ((extensionKey == "duration" and info[extensionKey] == 0) or
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(extensionKey == "comment" and not (1 <= len(info[extensionKey]) <= 255))):
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continue
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version = b"89a"
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break
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else:
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if im.info.get("version") == b"89a":
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version = b"89a"
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header = [
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b"GIF"+version + # signature + version
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o16(im.size[0]) + # canvas width
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o16(im.size[1]) # canvas height
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]
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palette_bytes, used_palette_colors = _get_palette_bytes(im, palette, info)
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# Logical Screen Descriptor
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color_table_size = _get_color_table_size(palette_bytes)
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# size of global color table + global color table flag
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header.append(o8(color_table_size + 128)) # packed fields
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# background + reserved/aspect
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if info and "background" in info:
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background = info["background"]
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elif "background" in im.info:
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# This elif is redundant within GifImagePlugin
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# since im.info parameters are bundled into the info dictionary
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# However, external scripts may call getheader directly
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# So this maintains earlier behaviour
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background = im.info["background"]
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else:
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background = 0
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header.append(o8(background) + o8(0))
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# end of Logical Screen Descriptor
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# Header + Logical Screen Descriptor + Global Color Table
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header.append(_get_header_palette(palette_bytes))
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return header, used_palette_colors
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def getdata(im, offset=(0, 0), **params):
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"""Return a list of strings representing this image.
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The first string is a local image header, the rest contains
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encoded image data."""
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class Collector(object):
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data = []
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def write(self, data):
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self.data.append(data)
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im.load() # make sure raster data is available
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fp = Collector()
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try:
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im.encoderinfo = params
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# local image header
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_get_local_header(fp, im, offset, 0)
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ImageFile._save(im, fp, [("gif", (0, 0)+im.size, 0, RAWMODE[im.mode])])
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fp.write(b"\0") # end of image data
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finally:
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del im.encoderinfo
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return fp.data
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# --------------------------------------------------------------------
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# Registry
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Image.register_open(GifImageFile.format, GifImageFile, _accept)
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Image.register_save(GifImageFile.format, _save)
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Image.register_save_all(GifImageFile.format, _save_all)
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Image.register_extension(GifImageFile.format, ".gif")
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Image.register_mime(GifImageFile.format, "image/gif")
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#
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# Uncomment the following line if you wish to use NETPBM/PBMPLUS
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# instead of the built-in "uncompressed" GIF encoder
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# Image.register_save(GifImageFile.format, _save_netpbm)
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