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Added setting to convert to RGB only at a different palette

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This commit is contained in:
Andrew Murray 2022-03-22 20:28:49 +11:00
parent 66bb2bd5e8
commit ce8c682748
6 changed files with 164 additions and 91 deletions
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65
Tests/test_file_gif.py
View File

@ -79,15 +79,37 @@ def test_l_mode_subsequent_frames():
def test_strategy():
with Image.open(TEST_GIF) as im:
expected = im.convert("RGB")
with Image.open("Tests/images/chi.gif") as im:
expected_zero = im.convert("RGB")
GifImagePlugin.PALETTE_TO_RGB = GifImagePlugin.ModeStrategy.ALWAYS
with Image.open(TEST_GIF) as im:
assert im.mode == "RGB"
assert_image_equal(im, expected)
im.seek(1)
expected_one = im.convert("RGB")
GifImagePlugin.PALETTE_TO_RGB = GifImagePlugin.ModeStrategy.AFTER_FIRST
try:
GifImagePlugin.PALETTE_TO_RGB = GifImagePlugin.ModeStrategy.ALWAYS
with Image.open("Tests/images/chi.gif") as im:
assert im.mode == "RGB"
assert_image_equal(im, expected_zero)
GifImagePlugin.PALETTE_TO_RGB = (
GifImagePlugin.ModeStrategy.DIFFERENT_PALETTE_ONLY
)
# Stay in P mode with only a global palette
with Image.open("Tests/images/chi.gif") as im:
assert im.mode == "P"
im.seek(1)
assert im.mode == "P"
assert_image_equal(im.convert("RGB"), expected_one)
# Change to RGB mode when a frame has an individual palette
with Image.open("Tests/images/iss634.gif") as im:
assert im.mode == "P"
im.seek(1)
assert im.mode == "RGB"
finally:
GifImagePlugin.PALETTE_TO_RGB = GifImagePlugin.ModeStrategy.AFTER_FIRST
def test_optimize():
@ -414,12 +436,29 @@ def test_dispose_background_transparency():
assert px[35, 30][3] == 0
def test_transparent_dispose():
expected_colors = [
(2, 1, 2),
((0, 255, 24, 255), (0, 0, 255, 255), (0, 255, 24, 255)),
((0, 0, 0, 0), (0, 0, 255, 255), (0, 0, 0, 0)),
]
@pytest.mark.parametrize(
"mode_strategy, expected_colors",
(
(
GifImagePlugin.ModeStrategy.DIFFERENT_PALETTE_ONLY,
(
(2, 1, 2),
(0, 1, 0),
(2, 1, 2),
),
),
(
GifImagePlugin.ModeStrategy.AFTER_FIRST,
(
(2, 1, 2),
((0, 255, 24, 255), (0, 0, 255, 255), (0, 255, 24, 255)),
((0, 0, 0, 0), (0, 0, 255, 255), (0, 0, 0, 0)),
),
),
),
)
def test_transparent_dispose(mode_strategy, expected_colors):
GifImagePlugin.PALETTE_TO_RGB = mode_strategy
with Image.open("Tests/images/transparent_dispose.gif") as img:
for frame in range(3):
img.seek(frame)

16
docs/handbook/image-file-formats.rst
View File

@ -110,13 +110,25 @@ images. Seeking to later frames in a ``P`` image will change the image to
``RGB`` (or ``RGBA`` if the first frame had transparency). ``L`` images will
stay in ``L`` mode (or change to ``LA`` if the first frame had transparency).
If you would prefer the first ``P`` image frame to be ``RGB``, so that ``P``
frames are always converted to ``RGB`` or ``RGBA`` mode, there is a setting
``P`` mode images are changed to ``RGB`` because each frame of a GIF may
introduce up to 256 colors. Because ``P`` can only have up to 256 colors, the
image is converted to handle all of the colors.
If you would prefer the first ``P`` image frame to be ``RGB`` as well, so that
every ``P`` frame is converted to ``RGB`` or ``RGBA`` mode, there is a setting
available::
from PIL import GifImagePlugin
GifImagePlugin.PALETTE_TO_RGB = GifImagePlugin.ModeStrategy.ALWAYS
GIF frames do not always contain individual palettes however. If there is only
a global palette, then all of the colors can fit within ``P`` mode. If you would
prefer the frames to be kept as ``P`` in that case, there is also a setting
available::
from PIL import GifImagePlugin
GifImagePlugin.PALETTE_TO_RGB = GifImagePlugin.ModeStrategy.DIFFERENT_PALETTE_ONLY
The :py:meth:`~PIL.Image.open` method sets the following
:py:attr:`~PIL.Image.Image.info` properties:

131
src/PIL/GifImagePlugin.py
View File

@ -39,6 +39,7 @@ from ._binary import o16le as o16
class ModeStrategy(IntEnum):
AFTER_FIRST = 0
ALWAYS = 1
DIFFERENT_PALETTE_ONLY = 2
PALETTE_TO_RGB = ModeStrategy.AFTER_FIRST
@ -152,7 +153,6 @@ class GifImageFile(ImageFile.ImageFile):
# 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.disposal_method = 0
@ -180,33 +180,12 @@ class GifImageFile(ImageFile.ImageFile):
self.tile = []
if update_image:
if self.__frame == 1:
self.pyaccess = None
if self.mode == "P":
if "transparency" in self.info:
self.im.putpalettealpha(self.info["transparency"], 0)
self.im = self.im.convert("RGBA", Image.Dither.FLOYDSTEINBERG)
self.mode = "RGBA"
del self.info["transparency"]
else:
self.mode = "RGB"
self.im = self.im.convert("RGB", Image.Dither.FLOYDSTEINBERG)
elif "transparency" in self.info:
self.im = self.im.convert_transparent(
"LA", self.info["transparency"]
)
self.mode = "LA"
del self.info["transparency"]
if self.dispose:
self.im.paste(self.dispose, self.dispose_extent)
palette = None
info = {}
frame_transparency = None
interlace = None
frame_dispose_extent = None
while True:
if not s:
@ -273,7 +252,7 @@ class GifImageFile(ImageFile.ImageFile):
x1, y1 = x0 + i16(s, 4), y0 + i16(s, 6)
if x1 > self.size[0] or y1 > self.size[1]:
self._size = max(x1, self.size[0]), max(y1, self.size[1])
self.dispose_extent = x0, y0, x1, y1
frame_dispose_extent = x0, y0, x1, y1
flags = s[8]
interlace = (flags & 64) != 0
@ -298,15 +277,48 @@ class GifImageFile(ImageFile.ImageFile):
if not update_image:
return
frame_palette = palette or self.global_palette
if self.dispose:
self.im.paste(self.dispose, self.dispose_extent)
self._frame_palette = palette or self.global_palette
if frame == 0:
if self._frame_palette:
self.mode = "RGB" if PALETTE_TO_RGB == ModeStrategy.ALWAYS else "P"
else:
self.mode = "L"
if not palette and self.global_palette:
from copy import copy
palette = copy(self.global_palette)
self.palette = palette
else:
self._frame_transparency = frame_transparency
if self.mode == "P":
if PALETTE_TO_RGB != ModeStrategy.DIFFERENT_PALETTE_ONLY or palette:
self.pyaccess = None
if "transparency" in self.info:
self.im.putpalettealpha(self.info["transparency"], 0)
self.im = self.im.convert("RGBA", Image.Dither.FLOYDSTEINBERG)
self.mode = "RGBA"
del self.info["transparency"]
else:
self.mode = "RGB"
self.im = self.im.convert("RGB", Image.Dither.FLOYDSTEINBERG)
elif self.mode == "L" and "transparency" in self.info:
self.pyaccess = None
self.im = self.im.convert_transparent("LA", self.info["transparency"])
self.mode = "LA"
del self.info["transparency"]
def _rgb(color):
if frame_palette:
color = tuple(frame_palette.palette[color * 3 : color * 3 + 3])
if self._frame_palette:
color = tuple(self._frame_palette.palette[color * 3 : color * 3 + 3])
else:
color = (color, color, color)
return color
self.dispose_extent = frame_dispose_extent
try:
if self.disposal_method < 2:
# do not dispose or none specified
@ -321,13 +333,17 @@ class GifImageFile(ImageFile.ImageFile):
Image._decompression_bomb_check(dispose_size)
# by convention, attempt to use transparency first
dispose_mode = "P"
color = self.info.get("transparency", frame_transparency)
if color is not None:
dispose_mode = "RGBA"
color = _rgb(color) + (0,)
if self.mode in ("RGB", "RGBA"):
dispose_mode = "RGBA"
color = _rgb(color) + (0,)
else:
dispose_mode = "RGB"
color = _rgb(self.info.get("background", 0))
color = self.info.get("background", 0)
if self.mode in ("RGB", "RGBA"):
dispose_mode = "RGB"
color = _rgb(color)
self.dispose = Image.core.fill(dispose_mode, dispose_size, color)
else:
# replace with previous contents
@ -339,21 +355,28 @@ class GifImageFile(ImageFile.ImageFile):
dispose_size = (x1 - x0, y1 - y0)
Image._decompression_bomb_check(dispose_size)
self.dispose = Image.core.fill(
"RGBA", dispose_size, _rgb(frame_transparency) + (0,)
)
dispose_mode = "P"
color = frame_transparency
if self.mode in ("RGB", "RGBA"):
dispose_mode = "RGBA"
color = _rgb(frame_transparency) + (0,)
self.dispose = Image.core.fill(dispose_mode, dispose_size, color)
except AttributeError:
pass
if interlace is not None:
if frame == 0 and frame_transparency is not None:
self.info["transparency"] = frame_transparency
transparency = -1
if frame_transparency is not None:
if frame == 0:
self.info["transparency"] = frame_transparency
elif self.mode not in ("RGB", "RGBA", "LA"):
transparency = frame_transparency
self.tile = [
(
"gif",
(x0, y0, x1, y1),
self.__offset,
(bits, interlace),
(bits, interlace, transparency),
)
]
@ -363,35 +386,22 @@ class GifImageFile(ImageFile.ImageFile):
elif k in self.info:
del self.info[k]
if frame == 0:
if frame_palette:
self.mode = "RGB" if PALETTE_TO_RGB == ModeStrategy.ALWAYS else "P"
else:
self.mode = "L"
if not palette and self.global_palette:
from copy import copy
palette = copy(self.global_palette)
self.palette = palette
else:
self._frame_transparency = frame_transparency
self._frame_palette = frame_palette
def load_prepare(self):
self.mode = "P" if self._frame_palette else "L"
temp_mode = "P" if self._frame_palette else "L"
self._prev_im = None
if self.__frame == 0:
if "transparency" in self.info:
self.im = Image.core.fill(
self.mode, self.size, self.info["transparency"]
temp_mode, self.size, self.info["transparency"]
)
else:
elif self.mode in ("RGB", "RGBA", "LA"):
self._prev_im = self.im
if self._frame_palette:
self.im = Image.core.fill("P", self.size, self._frame_transparency or 0)
self.im.putpalette(*self._frame_palette.getdata())
else:
self.im = None
self.mode = temp_mode
self._frame_palette = None
super().load_prepare()
@ -402,17 +412,18 @@ class GifImageFile(ImageFile.ImageFile):
self.mode = "RGB"
self.im = self.im.convert("RGB", Image.Dither.FLOYDSTEINBERG)
return
if self.mode == "P":
if self.mode == "P" and self._prev_im:
if self._frame_transparency is not None:
self.im.putpalettealpha(self._frame_transparency, 0)
frame_im = self.im.convert("RGBA")
else:
frame_im = self.im.convert("RGB")
elif self.mode == "L" and self._frame_transparency is not None:
frame_im = self.im.convert_transparent("LA", self._frame_transparency)
else:
if self._frame_transparency is not None:
frame_im = self.im.convert_transparent("LA", self._frame_transparency)
else:
frame_im = self.im
if not self._prev_im:
return
frame_im = self.im
frame_im = self._crop(frame_im, self.dispose_extent)
self.im = self._prev_im

4
src/decode.c
View File

@ -433,7 +433,8 @@ PyImaging_GifDecoderNew(PyObject *self, PyObject *args) {
char *mode;
int bits = 8;
int interlace = 0;
if (!PyArg_ParseTuple(args, "s|ii", &mode, &bits, &interlace)) {
int transparency = -1;
if (!PyArg_ParseTuple(args, "s|iii", &mode, &bits, &interlace, &transparency)) {
return NULL;
}
@ -451,6 +452,7 @@ PyImaging_GifDecoderNew(PyObject *self, PyObject *args) {
((GIFDECODERSTATE *)decoder->state.context)->bits = bits;
((GIFDECODERSTATE *)decoder->state.context)->interlace = interlace;
((GIFDECODERSTATE *)decoder->state.context)->transparency = transparency;
return (PyObject *)decoder;
}

3
src/libImaging/Gif.h
View File

@ -30,6 +30,9 @@ typedef struct {
*/
int interlace;
/* The transparent palette index, or -1 for no transparency */
int transparency;
/* PRIVATE CONTEXT (set by decoder) */
/* Interlace parameters */

36
src/libImaging/GifDecode.c
View File

@ -248,27 +248,33 @@ ImagingGifDecode(Imaging im, ImagingCodecState state, UINT8 *buffer, Py_ssize_t
/* To squeeze some extra pixels out of this loop, we test for
some common cases and handle them separately. */
if (i == 1) {
if (state->x < state->xsize - 1) {
/* Single pixel, not at the end of the line. */
*out++ = p[0];
state->x++;
/* This cannot be used if there is transparency */
if (context->transparency == -1) {
if (i == 1) {
if (state->x < state->xsize - 1) {
/* Single pixel, not at the end of the line. */
*out++ = p[0];
state->x++;
continue;
}
} else if (state->x + i <= state->xsize) {
/* This string fits into current line. */
memcpy(out, p, i);
out += i;
state->x += i;
if (state->x == state->xsize) {
NEWLINE(state, context);
}
continue;
}
} else if (state->x + i <= state->xsize) {
/* This string fits into current line. */
memcpy(out, p, i);
out += i;
state->x += i;
if (state->x == state->xsize) {
NEWLINE(state, context);
}
continue;
}
/* No shortcut, copy pixel by pixel */
for (c = 0; c < i; c++) {
*out++ = p[c];
if (p[c] != context->transparency) {
*out = p[c];
}
out++;
if (++state->x >= state->xsize) {
NEWLINE(state, context);
}