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479 lines
14 KiB
Python
479 lines
14 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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__version__ = "0.9"
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from PIL import Image, ImageFile, ImagePalette, _binary
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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.seek(0) # get ready to read first frame
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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.__frame = -1
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self.__fp.seek(self.__rewind)
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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 = self.dispose
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self.dispose = None
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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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try:
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# disposal methods
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if flags & 8:
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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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elif flags & 16:
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# replace with previous contents
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self.dispose = self.im.copy()
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except (AttributeError, KeyError):
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pass
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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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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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if not self.tile:
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# self.__fp = None
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raise EOFError("no more images in GIF file")
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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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# --------------------------------------------------------------------
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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 _save(im, fp, filename):
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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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try:
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rawmode = RAWMODE[im.mode]
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imOut = im
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except KeyError:
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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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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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imOut = im.convert("P", palette=1, colors=palette_size)
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rawmode = "P"
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else:
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imOut = im.convert("L")
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rawmode = "L"
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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 im.encoderinfo["optimize"]:
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# When the mode is L, and we optimize, we end up with
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# im.mode == P and rawmode = L, which fails.
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# If we're optimizing the palette, we're going to be
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# in a rawmode of P anyway.
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rawmode = 'P'
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header, usedPaletteColors = getheader(imOut, palette, im.encoderinfo)
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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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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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if interlace:
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flags = flags | 64
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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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transparentColorExists = True
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# adjust the transparency index after optimize
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if usedPaletteColors is not None and len(usedPaletteColors) < 256:
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for i in range(len(usedPaletteColors)):
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if usedPaletteColors[i] == transparency:
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transparency = i
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transparentColorExists = True
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break
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else:
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transparentColorExists = False
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# transparency extension block
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if transparentColorExists:
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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(1) + # transparency info present
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o16(0) + # duration
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o8(transparency) # transparency index
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+ o8(0))
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# local image header
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fp.write(b"," +
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o16(0) + o16(0) + # bounding box
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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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o8(8)) # bits
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imOut.encoderconfig = (8, interlace)
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ImageFile._save(imOut, fp, [("gif", (0,0)+im.size, 0, rawmode)])
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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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try:
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fp.flush()
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except: pass
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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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file = im._dump()
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if im.mode != "RGB":
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os.system("ppmtogif %s >%s" % (file, filename))
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else:
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os.system("ppmquant 256 %s | ppmtogif >%s" % (file, filename))
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try: os.unlink(file)
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except: pass
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# --------------------------------------------------------------------
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# GIF utilities
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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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optimize = info and info.get("optimize", 0)
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# Header Block
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# http://www.matthewflickinger.com/lab/whatsinagif/bits_and_bytes.asp
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header = [
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b"GIF87a" + # 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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if im.mode == "P":
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if palette and isinstance(palette, bytes):
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sourcePalette = palette[:768]
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else:
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sourcePalette = 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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sourcePalette = palette[:768]
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else:
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sourcePalette = bytearray([i//3 for i in range(768)])
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usedPaletteColors = paletteBytes = None
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if optimize:
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usedPaletteColors = []
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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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usedPaletteColors.append(i)
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i += 1
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# create the new palette if not every color is used
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if len(usedPaletteColors) < 256:
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paletteBytes = b""
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newPositions = {}
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i = 0
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# pick only the used colors from the palette
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for oldPosition in usedPaletteColors:
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paletteBytes += sourcePalette[oldPosition*3:oldPosition*3+3]
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newPositions[oldPosition] = i
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i += 1
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# replace the palette color id of all pixel with the new id
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imageBytes = bytearray(im.tobytes())
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for i in range(len(imageBytes)):
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imageBytes[i] = newPositions[imageBytes[i]]
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im.frombytes(bytes(imageBytes))
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newPaletteBytes = paletteBytes + (768 - len(paletteBytes)) * b'\x00'
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im.putpalette(newPaletteBytes)
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im.palette = ImagePalette.ImagePalette("RGB", palette = paletteBytes, size = len(paletteBytes))
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if not paletteBytes:
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paletteBytes = sourcePalette
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# Logical Screen Descriptor
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# calculate the palette size for the header
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import math
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colorTableSize = int(math.ceil(math.log(len(paletteBytes)//3, 2)))-1
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if colorTableSize < 0: colorTableSize = 0
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# size of global color table + global color table flag
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header.append(o8(colorTableSize + 128))
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# background + reserved/aspect
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header.append(o8(0) + o8(0))
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# end of Logical Screen Descriptor
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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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actualTargetSizeDiff = (2<<colorTableSize) - len(paletteBytes)//3
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if actualTargetSizeDiff > 0:
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paletteBytes += o8(0) * 3 * actualTargetSizeDiff
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# Header + Logical Screen Descriptor + Global Color Table
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header.append(paletteBytes)
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return header, usedPaletteColors
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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:
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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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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(0) + # flags
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o8(8)) # bits
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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_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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