408 lines
11 KiB
Python
408 lines
11 KiB
Python
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#
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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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import Image, ImageFile, ImagePalette
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# --------------------------------------------------------------------
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# Helpers
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def i16(c):
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return ord(c[0]) + (ord(c[1])<<8)
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def o16(i):
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return chr(i&255) + chr(i>>8&255)
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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 ["GIF87a", "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 ord(s):
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return self.fp.read(ord(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 ["GIF87a", "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 = ord(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"] = ord(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 (chr(i/3) == p[i] == p[i+1] == 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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self.palette = self.global_palette
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while 1:
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s = self.fp.read(1)
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if not s or s == ";":
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break
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elif s == "!":
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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 ord(s) == 249:
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#
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# graphic control extension
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#
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flags = ord(block[0])
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if flags & 1:
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self.info["transparency"] = ord(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 ord(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] == "NETSCAPE2.0":
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block = self.data()
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if len(block) >= 3 and ord(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 == ",":
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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 = ord(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 = ord(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`" % ord(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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imOut = im.convert("P")
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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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for s in getheader(imOut, im.encoderinfo):
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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 extension block
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fp.write("!" +
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chr(249) + # extension intro
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chr(4) + # length
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chr(1) + # transparency info present
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o16(0) + # duration
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chr(int(transparency)) # transparency index
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+ chr(0))
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# local image header
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fp.write("," +
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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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chr(flags) + # flags
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chr(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("\0") # end of image data
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fp.write(";") # 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, 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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s = [
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"GIF87a" + # magic
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o16(im.size[0]) + # size
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o16(im.size[1]) +
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chr(7 + 128) + # flags: bits + palette
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chr(0) + # background
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chr(0) # reserved/aspect
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]
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if optimize:
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# minimize color palette
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i = 0
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maxcolor = 0
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for count in im.histogram():
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if count:
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maxcolor = i
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i = i + 1
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else:
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maxcolor = 256
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# global palette
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if im.mode == "P":
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# colour palette
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s.append(im.im.getpalette("RGB")[:maxcolor*3])
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else:
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# greyscale
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for i in range(maxcolor):
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s.append(chr(i) * 3)
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return s
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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("," +
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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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chr(0) + # flags
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chr(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("\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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