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Added support for PPM arbitrary maxval in plain formats

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This commit is contained in:
Andrew Murray 2022-06-13 19:55:25 +10:00
parent 5051a29a4e
commit c4d51fb268
2 changed files with 55 additions and 44 deletions
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16
Tests/test_file_ppm.py
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@ -22,6 +22,21 @@ def test_sanity():
@pytest.mark.parametrize( @pytest.mark.parametrize(
"data, mode, pixels", "data, mode, pixels",
( (
(b"P2 3 1 4 0 2 4", "L", (0, 128, 255)),
(b"P2 3 1 257 0 128 257", "I", (0, 32640, 65535)),
# P3 with maxval < 255
(
b"P3 3 1 17 0 1 2 8 9 10 15 16 17",
"RGB",
((0, 15, 30), (120, 135, 150), (225, 240, 255)),
),
# P3 with maxval > 255
# Scale down to 255, since there is no RGB mode with more than 8-bit
(
b"P3 3 1 257 0 1 2 128 129 130 256 257 257",
"RGB",
((0, 1, 2), (127, 128, 129), (254, 255, 255)),
),
(b"P5 3 1 4 \x00\x02\x04", "L", (0, 128, 255)), (b"P5 3 1 4 \x00\x02\x04", "L", (0, 128, 255)),
(b"P5 3 1 257 \x00\x00\x00\x80\x01\x01", "I", (0, 32640, 65535)), (b"P5 3 1 257 \x00\x00\x00\x80\x01\x01", "I", (0, 32640, 65535)),
# P6 with maxval < 255 # P6 with maxval < 255
@ -35,7 +50,6 @@ def test_sanity():
), ),
), ),
# P6 with maxval > 255 # P6 with maxval > 255
# Scale down to 255, since there is no RGB mode with more than 8-bit
( (
b"P6 3 1 257 \x00\x00\x00\x01\x00\x02" b"P6 3 1 257 \x00\x00\x00\x01\x00\x02"
b"\x00\x80\x00\x81\x00\x82\x01\x00\x01\x01\xFF\xFF", b"\x00\x80\x00\x81\x00\x82\x01\x00\x01\x01\xFF\xFF",

83
src/PIL/PpmImagePlugin.py
View File

@ -105,6 +105,8 @@ class PpmImageFile(ImageFile.ImageFile):
maxval = None maxval = None
decoder_name = "raw" decoder_name = "raw"
if magic_number in (b"P1", b"P2", b"P3"):
decoder_name = "ppm_plain"
for ix in range(3): for ix in range(3):
token = int(self._read_token()) token = int(self._read_token())
if ix == 0: # token is the x size if ix == 0: # token is the x size
@ -126,14 +128,13 @@ class PpmImageFile(ImageFile.ImageFile):
if maxval > 255 and mode == "L": if maxval > 255 and mode == "L":
self.mode = "I" self.mode = "I"
# If maxval matches a bit depth, use the raw decoder directly if decoder_name != "ppm_plain":
if maxval == 65535 and mode == "L": # If maxval matches a bit depth, use the raw decoder directly
rawmode = "I;16B" if maxval == 65535 and mode == "L":
elif maxval != 255: rawmode = "I;16B"
decoder_name = "ppm" elif maxval != 255:
decoder_name = "ppm"
if magic_number in (b"P1", b"P2", b"P3"):
decoder_name = "ppm_plain"
args = (rawmode, 0, 1) if decoder_name == "raw" else (rawmode, maxval) args = (rawmode, 0, 1) if decoder_name == "raw" else (rawmode, maxval)
self._size = xsize, ysize self._size = xsize, ysize
self.tile = [(decoder_name, (0, 0, xsize, ysize), self.fp.tell(), args)] self.tile = [(decoder_name, (0, 0, xsize, ysize), self.fp.tell(), args)]
@ -156,7 +157,7 @@ class PpmPlainDecoder(ImageFile.PyDecoder):
def _ignore_comments(self, block): def _ignore_comments(self, block):
""" """
Deletes comments from block. Delete comments from block.
If comment does not end in this block, raises a flag. If comment does not end in this block, raises a flag.
""" """
comment_spans = False comment_spans = False
@ -176,14 +177,14 @@ class PpmPlainDecoder(ImageFile.PyDecoder):
def _decode_bitonal(self): def _decode_bitonal(self):
""" """
This is a separate method because the plain PBM format all data tokens This is a separate method because in the plain PBM format, all data tokens are
are exactly one byte, and so the inter-token whitespace is optional. exactly one byte, so the inter-token whitespace is optional.
""" """
decoded_data = bytearray() data = bytearray()
total_bytes = self.state.xsize * self.state.ysize total_bytes = self.state.xsize * self.state.ysize
comment_spans = False comment_spans = False
while len(decoded_data) != total_bytes: while len(data) != total_bytes:
block = self._read_block() # read next block block = self._read_block() # read next block
if not block: if not block:
# eof # eof
@ -193,7 +194,7 @@ class PpmPlainDecoder(ImageFile.PyDecoder):
comment_end = self._find_comment_end(block) comment_end = self._find_comment_end(block)
if comment_end != -1: # comment ends in this block if comment_end != -1: # comment ends in this block
block = block[comment_end + 1 :] # delete tail of previous comment block = block[comment_end + 1 :] # delete tail of previous comment
comment_spans = False break
else: # comment spans whole block else: # comment spans whole block
block = self._read_block() block = self._read_block()
@ -203,19 +204,21 @@ class PpmPlainDecoder(ImageFile.PyDecoder):
for token in tokens: for token in tokens:
if token not in (48, 49): if token not in (48, 49):
raise ValueError(f"Invalid token for this mode: {bytes([token])}") raise ValueError(f"Invalid token for this mode: {bytes([token])}")
decoded_data = (decoded_data + tokens)[:total_bytes] data = (data + tokens)[:total_bytes]
invert = bytes.maketrans(b"01", b"\xFF\x00") invert = bytes.maketrans(b"01", b"\xFF\x00")
return decoded_data.translate(invert) return data.translate(invert)
def _decode_blocks(self, channels, depth, maxval): def _decode_blocks(self, maxval):
decoded_data = bytearray() data = bytearray()
max_len = 10 max_len = 10
bytes_per_sample = depth // 8 out_byte_count = 4 if self.mode == "I" else 1
total_bytes = self.state.xsize * self.state.ysize * channels * bytes_per_sample out_max = 65535 if self.mode == "I" else 255
bands = Image.getmodebands(self.mode)
total_bytes = self.state.xsize * self.state.ysize * bands * out_byte_count
comment_spans = False comment_spans = False
half_token = False half_token = False
while len(decoded_data) != total_bytes: while len(data) != total_bytes:
block = self._read_block() # read next block block = self._read_block() # read next block
if not block: if not block:
if half_token: if half_token:
@ -251,31 +254,24 @@ class PpmPlainDecoder(ImageFile.PyDecoder):
raise ValueError( raise ValueError(
f"Token too long found in data: {token[:max_len + 1]}" f"Token too long found in data: {token[:max_len + 1]}"
) )
token = int(token) value = int(token)
if token > maxval: if value > maxval:
raise ValueError(f"Channel value too large for this mode: {token}") raise ValueError(f"Channel value too large for this mode: {value}")
decoded_data += token.to_bytes(bytes_per_sample, "big") value = round(value / maxval * out_max)
if len(decoded_data) == total_bytes: # finished! data += o32(value) if self.mode == "I" else o8(value)
if len(data) == total_bytes: # finished!
break break
return decoded_data return data
def decode(self, buffer): def decode(self, buffer):
rawmode, maxval = self.args
if self.mode == "1": if self.mode == "1":
decoded_data = self._decode_bitonal() data = self._decode_bitonal()
rawmode = "1;8" rawmode = "1;8"
elif self.mode == "L": else:
decoded_data = self._decode_blocks(1, 8, maxval) maxval = self.args[-1]
elif self.mode == "I": data = self._decode_blocks(maxval)
if rawmode == "I;16B": rawmode = "I;32" if self.mode == "I" else self.mode
decoded_data = self._decode_blocks(1, 16, maxval) self.set_as_raw(bytes(data), rawmode)
elif rawmode == "I;32B":
decoded_data = self._decode_blocks(1, 32, maxval)
elif self.mode == "RGB":
decoded_data = self._decode_blocks(3, 8, maxval)
self.set_as_raw(bytes(decoded_data), rawmode)
return -1, 0 return -1, 0
@ -284,7 +280,7 @@ class PpmDecoder(ImageFile.PyDecoder):
def decode(self, buffer): def decode(self, buffer):
data = bytearray() data = bytearray()
maxval = min(self.args[-1], 65535) maxval = self.args[-1]
in_byte_count = 1 if maxval < 256 else 2 in_byte_count = 1 if maxval < 256 else 2
out_byte_count = 4 if self.mode == "I" else 1 out_byte_count = 4 if self.mode == "I" else 1
out_max = 65535 if self.mode == "I" else 255 out_max = 65535 if self.mode == "I" else 255
@ -301,7 +297,7 @@ class PpmDecoder(ImageFile.PyDecoder):
value = min(out_max, round(value / maxval * out_max)) value = min(out_max, round(value / maxval * out_max))
data += o32(value) if self.mode == "I" else o8(value) data += o32(value) if self.mode == "I" else o8(value)
rawmode = "I;32" if self.mode == "I" else self.mode rawmode = "I;32" if self.mode == "I" else self.mode
self.set_as_raw(bytes(data), (rawmode, 0, 1)) self.set_as_raw(bytes(data), rawmode)
return -1, 0 return -1, 0
@ -337,11 +333,12 @@ def _save(im, fp, filename):
# #
# -------------------------------------------------------------------- # --------------------------------------------------------------------
Image.register_decoder("ppm_plain", PpmPlainDecoder)
Image.register_open(PpmImageFile.format, PpmImageFile, _accept) Image.register_open(PpmImageFile.format, PpmImageFile, _accept)
Image.register_save(PpmImageFile.format, _save) Image.register_save(PpmImageFile.format, _save)
Image.register_decoder("ppm", PpmDecoder) Image.register_decoder("ppm", PpmDecoder)
Image.register_decoder("ppm_plain", PpmPlainDecoder)
Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm"]) Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm"])