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Combined BMP RLE decoders #1

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merged 2 commits into from Oct 24, 2022
Merged

Combined BMP RLE decoders #1

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78430b9
Corrected BMP compression setting [ci skip]
radarhere Oct 22, 2022
6c8234b
Combined BMP RLE decoders
radarhere Oct 22, 2022
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4 changes: 2 additions & 2 deletions docs/handbook/image-file-formats.rst
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Expand Up @@ -56,8 +56,8 @@ The :py:meth:`~PIL.Image.open` method sets the following
:py:attr:`~PIL.Image.Image.info` properties:

**compression**
Set to ``bmp_rle8`` if the file is a 256-color run-length encoded image.
Set to ``bmp_rle4`` if the file is a 16-color run-length encoded image.
Set to 1 if the file is a 256-color run-length encoded image.
Set to 2 if the file is a 16-color run-length encoded image.

DDS
^^^
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113 changes: 34 additions & 79 deletions src/PIL/BmpImagePlugin.py
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Expand Up @@ -211,10 +211,8 @@ def _bitmap(self, header=0, offset=0):
elif file_info["compression"] == self.RAW:
if file_info["bits"] == 32 and header == 22: # 32-bit .cur offset
raw_mode, self.mode = "BGRA", "RGBA"
elif file_info["compression"] == self.RLE8:
decoder_name = "bmp_rle8"
elif file_info["compression"] == self.RLE4:
decoder_name = "bmp_rle4"
elif file_info["compression"] in (self.RLE8, self.RLE4):
decoder_name = "bmp_rle"
else:
raise OSError(f"Unsupported BMP compression ({file_info['compression']})")

Expand Down Expand Up @@ -252,16 +250,18 @@ def _bitmap(self, header=0, offset=0):

# ---------------------------- Finally set the tile data for the plugin
self.info["compression"] = file_info["compression"]
args = [raw_mode]
if decoder_name == "bmp_rle":
args.append(file_info["compression"] == self.RLE4)
else:
args.append(((file_info["width"] * file_info["bits"] + 31) >> 3) & (~3))
args.append(file_info["direction"])
self.tile = [
(
decoder_name,
(0, 0, file_info["width"], file_info["height"]),
offset or self.fp.tell(),
(
raw_mode,
((file_info["width"] * file_info["bits"] + 31) >> 3) & (~3),
file_info["direction"],
),
tuple(args),
)
]

Expand All @@ -278,10 +278,11 @@ def _open(self):
self._bitmap(offset=offset)


class BmpRle8Decoder(ImageFile.PyDecoder):
class BmpRleDecoder(ImageFile.PyDecoder):
_pulls_fd = True

def decode(self, buffer):
rle4 = self.args[1]
data = bytearray()
x = 0
while len(data) < self.state.xsize * self.state.ysize:
Expand All @@ -295,67 +296,19 @@ def decode(self, buffer):
if x + num_pixels > self.state.xsize:
# Too much data for row
num_pixels = max(0, self.state.xsize - x)
data += byte * num_pixels
x += num_pixels
else:
if byte[0] == 0:
# end of line
while len(data) % self.state.xsize != 0:
data += b"\x00"
x = 0
elif byte[0] == 1:
# end of bitmap
break
elif byte[0] == 2:
# delta
bytes_read = self.fd.read(2)
if len(bytes_read) < 2:
break
right, up = self.fd.read(2)
data += b"\x00" * (right + up * self.state.xsize)
x = len(data) % self.state.xsize
if rle4:
first_pixel = o8(byte[0] >> 4)
second_pixel = o8(byte[0] & 0x0F)
for index in range(num_pixels):
if index % 2 == 0:
data += first_pixel
else:
data += second_pixel
else:
# absolute mode
bytes_read = self.fd.read(byte[0])
data += bytes_read
if len(bytes_read) < byte[0]:
break
x += byte[0]

# align to 16-bit word boundary
if self.fd.tell() % 2 != 0:
self.fd.seek(1, os.SEEK_CUR)
rawmode = "L" if self.mode == "L" else "P"
self.set_as_raw(bytes(data), (rawmode, 0, self.args[-1]))
return -1, 0


class BmpRle4Decoder(ImageFile.PyDecoder):
_pulls_fd = True

def decode(self, buffer):
data = bytearray()
x = 0
while len(data) < self.state.xsize * self.state.ysize:
pixels = self.fd.read(1)
byte = self.fd.read(1)
if not pixels or not byte:
break
num_pixels = pixels[0]
if num_pixels:
# encoded mode
if x + num_pixels > self.state.xsize:
# Too much data for row
num_pixels = max(0, self.state.xsize - x)
first_pixel = o8(byte[0] >> 4)
second_pixel = o8(byte[0] & 0x0F)
for index in range(num_pixels):
if index % 2 == 0:
data += first_pixel
else:
data += second_pixel
data += byte * num_pixels
x += num_pixels
else:
# absolute mode
if byte[0] == 0:
# end of line
while len(data) % self.state.xsize != 0:
Expand All @@ -373,15 +326,18 @@ def decode(self, buffer):
data += b"\x00" * (right + up * self.state.xsize)
x = len(data) % self.state.xsize
else:
# absolute mode (2 pixels per byte)
total_bytes_to_read = byte[0] // 2
bytes_read = self.fd.read(total_bytes_to_read)
for byte_read in bytes_read:
first_pixel = o8(byte_read >> 4)
data += first_pixel
second_pixel = o8(byte_read & 0x0F)
data += second_pixel
if len(bytes_read) < total_bytes_to_read:
if rle4:
# 2 pixels per byte
byte_count = byte[0] // 2
bytes_read = self.fd.read(byte_count)
for byte_read in bytes_read:
data += o8(byte_read >> 4)
data += o8(byte_read & 0x0F)
else:
byte_count = byte[0]
bytes_read = self.fd.read(byte_count)
data += bytes_read
Comment on lines +329 to +339
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The first two lines of code in each branch here are the same (other than the comment), so they could be pulled out of the if..else.

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The first line of the first branch is byte_count = byte[0] // 2 and the first line of the second branch is byte_count = byte[0]. As I noted elsewhere, // 2 isn't a comment, it's division.

if len(bytes_read) < byte_count:
break
x += byte[0]

Expand Down Expand Up @@ -498,8 +454,7 @@ def _save(im, fp, filename, bitmap_header=True):

Image.register_mime(BmpImageFile.format, "image/bmp")

Image.register_decoder("bmp_rle8", BmpRle8Decoder)
Image.register_decoder("bmp_rle4", BmpRle4Decoder)
Image.register_decoder("bmp_rle", BmpRleDecoder)

Image.register_open(DibImageFile.format, DibImageFile, _dib_accept)
Image.register_save(DibImageFile.format, _dib_save)
Expand Down