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GIF seek performance improvements #6077

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merged 4 commits into from
Mar 11, 2022
Merged

GIF seek performance improvements #6077

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73cf28c
If GIF has already seeked past first frame, it is animated
radarhere Feb 21, 2022
590c616
If next byte ends the GIF, stay on the current frame
radarhere Feb 21, 2022
f854676
Do not update images during n_frames or is_animated seeking
radarhere Feb 21, 2022
ca6724b
Merge branch 'main' into gif
radarhere Mar 10, 2022
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70 changes: 42 additions & 28 deletions src/PIL/GifImagePlugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,7 @@ def n_frames(self):
current = self.tell()
try:
while True:
self.seek(self.tell() + 1)
self._seek(self.tell() + 1, False)
except EOFError:
self._n_frames = self.tell() + 1
self.seek(current)
Expand All @@ -110,14 +110,16 @@ def is_animated(self):
self._is_animated = self._n_frames != 1
else:
current = self.tell()

try:
self.seek(1)
if current:
self._is_animated = True
except EOFError:
self._is_animated = False
else:
try:
self._seek(1, False)
self._is_animated = True
except EOFError:
self._is_animated = False

self.seek(current)
self.seek(current)
return self._is_animated

def seek(self, frame):
Expand All @@ -135,7 +137,7 @@ def seek(self, frame):
self.seek(last_frame)
raise EOFError("no more images in GIF file") from e

def _seek(self, frame):
def _seek(self, frame, update_image=True):

if frame == 0:
# rewind
Expand All @@ -147,14 +149,11 @@ def _seek(self, frame):
self.disposal_method = 0
else:
# ensure that the previous frame was loaded
if self.tile:
if self.tile and update_image:
self.load()

if frame != self.__frame + 1:
raise ValueError(f"cannot seek to frame {frame}")
self.__frame = frame

self.tile = []

self.fp = self.__fp
if self.__offset:
Expand All @@ -164,19 +163,28 @@ def _seek(self, frame):
pass
self.__offset = 0

if self.__frame == 1:
self.pyaccess = None
if "transparency" in self.info:
self.mode = "RGBA"
self.im.putpalettealpha(self.info["transparency"], 0)
self.im = self.im.convert("RGBA", Image.Dither.FLOYDSTEINBERG)
s = self.fp.read(1)
if not s or s == b";":
raise EOFError

del self.info["transparency"]
else:
self.mode = "RGB"
self.im = self.im.convert("RGB", Image.Dither.FLOYDSTEINBERG)
if self.dispose:
self.im.paste(self.dispose, self.dispose_extent)
self.__frame = frame

self.tile = []

if update_image:
if self.__frame == 1:
self.pyaccess = None
if "transparency" in self.info:
self.mode = "RGBA"
self.im.putpalettealpha(self.info["transparency"], 0)
self.im = self.im.convert("RGBA", Image.Dither.FLOYDSTEINBERG)

del self.info["transparency"]
else:
self.mode = "RGB"
self.im = self.im.convert("RGB", Image.Dither.FLOYDSTEINBERG)
if self.dispose:
self.im.paste(self.dispose, self.dispose_extent)

palette = None

Expand All @@ -185,7 +193,8 @@ def _seek(self, frame):
interlace = None
while True:

s = self.fp.read(1)
if not s:
s = self.fp.read(1)
if not s or s == b";":
break

Expand Down Expand Up @@ -223,6 +232,7 @@ def _seek(self, frame):
else:
info["comment"] = block
block = self.data()
s = None
continue
elif s[0] == 255:
#
Expand Down Expand Up @@ -264,6 +274,13 @@ def _seek(self, frame):
else:
pass
# raise OSError, "illegal GIF tag `%x`" % s[0]
s = None

if interlace is None:
# self.__fp = None
raise EOFError
if not update_image:
return

frame_palette = palette or self.global_palette

Expand Down Expand Up @@ -323,9 +340,6 @@ def _rgb(color):
(bits, interlace),
)
]
else:
# self.__fp = None
raise EOFError

for k in ["duration", "comment", "extension", "loop"]:
if k in info:
Expand Down