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Pillow/PIL/GifImagePlugin.py
Andrew Murray 1b8d12b048 If only one frame, do not use image from sequence
2015-08-24 23:51:02 +10:00

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