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"""
Blizzard Mipmap Format (.blp)
Jerome Leclanche <[email protected]>
The contents of this file are hereby released in the public domain (CC0)
Full text of the CC0 license:
https://creativecommons.org/publicdomain/zero/1.0/
BLP1 files, used mostly in Warcraft III, are not fully supported.
All types of BLP2 files used in World of Warcraft are supported.
The BLP file structure consists of a header, up to 16 mipmaps of the
texture
Texture sizes must be powers of two, though the two dimensions do
not have to be equal; 512x256 is valid, but 512x200 is not.
The first mipmap (mipmap #0) is the full size image; each subsequent
mipmap halves both dimensions. The final mipmap should be 1x1.
BLP files come in many different flavours:
* JPEG-compressed (type == 0) - only supported for BLP1.
* RAW images (type == 1, encoding == 1). Each mipmap is stored as an
array of 8-bit values, one per pixel, left to right, top to bottom.
Each value is an index to the palette.
* DXT-compressed (type == 1, encoding == 2):
- DXT1 compression is used if alpha_encoding == 0.
- An additional alpha bit is used if alpha_depth == 1.
- DXT3 compression is used if alpha_encoding == 1.
- DXT5 compression is used if alpha_encoding == 7.
"""
from __future__ import annotations
import abc
import os
import struct
from enum import IntEnum
from io import BytesIO
from typing import IO
from . import Image, ImageFile
class Format(IntEnum):
JPEG = 0
class Encoding(IntEnum):
UNCOMPRESSED = 1
DXT = 2
UNCOMPRESSED_RAW_BGRA = 3
class AlphaEncoding(IntEnum):
DXT1 = 0
DXT3 = 1
DXT5 = 7
def unpack_565(i: int) -> tuple[int, int, int]:
return ((i >> 11) & 0x1F) << 3, ((i >> 5) & 0x3F) << 2, (i & 0x1F) << 3
def decode_dxt1(
data: bytes, alpha: bool = False
) -> tuple[bytearray, bytearray, bytearray, bytearray]:
"""
input: one "row" of data (i.e. will produce 4*width pixels)
"""
blocks = len(data) // 8 # number of blocks in row
ret = (bytearray(), bytearray(), bytearray(), bytearray())
for block_index in range(blocks):
# Decode next 8-byte block.
idx = block_index * 8
color0, color1, bits = struct.unpack_from("<HHI", data, idx)
r0, g0, b0 = unpack_565(color0)
r1, g1, b1 = unpack_565(color1)
# Decode this block into 4x4 pixels
# Accumulate the results onto our 4 row accumulators
for j in range(4):
for i in range(4):
# get next control op and generate a pixel
control = bits & 3
bits = bits >> 2
a = 0xFF
if control == 0:
r, g, b = r0, g0, b0
elif control == 1:
r, g, b = r1, g1, b1
elif control == 2:
if color0 > color1:
r = (2 * r0 + r1) // 3
g = (2 * g0 + g1) // 3
b = (2 * b0 + b1) // 3
else:
r = (r0 + r1) // 2
g = (g0 + g1) // 2
b = (b0 + b1) // 2
elif control == 3:
if color0 > color1:
r = (2 * r1 + r0) // 3
g = (2 * g1 + g0) // 3
b = (2 * b1 + b0) // 3
else:
r, g, b, a = 0, 0, 0, 0
if alpha:
ret[j].extend([r, g, b, a])
else:
ret[j].extend([r, g, b])
return ret
def decode_dxt3(data: bytes) -> tuple[bytearray, bytearray, bytearray, bytearray]:
"""
input: one "row" of data (i.e. will produce 4*width pixels)
"""
blocks = len(data) // 16 # number of blocks in row
ret = (bytearray(), bytearray(), bytearray(), bytearray())
for block_index in range(blocks):
idx = block_index * 16
block = data[idx : idx + 16]
# Decode next 16-byte block.
bits = struct.unpack_from("<8B", block)
color0, color1 = struct.unpack_from("<HH", block, 8)
(code,) = struct.unpack_from("<I", block, 12)
r0, g0, b0 = unpack_565(color0)
r1, g1, b1 = unpack_565(color1)
for j in range(4):
high = False # Do we want the higher bits?
for i in range(4):
alphacode_index = (4 * j + i) // 2
a = bits[alphacode_index]
if high:
high = False
a >>= 4
else:
high = True
a &= 0xF
a *= 17 # We get a value between 0 and 15
color_code = (code >> 2 * (4 * j + i)) & 0x03
if color_code == 0:
r, g, b = r0, g0, b0
elif color_code == 1:
r, g, b = r1, g1, b1
elif color_code == 2:
r = (2 * r0 + r1) // 3
g = (2 * g0 + g1) // 3
b = (2 * b0 + b1) // 3
elif color_code == 3:
r = (2 * r1 + r0) // 3
g = (2 * g1 + g0) // 3
b = (2 * b1 + b0) // 3
ret[j].extend([r, g, b, a])
return ret
def decode_dxt5(data: bytes) -> tuple[bytearray, bytearray, bytearray, bytearray]:
"""
input: one "row" of data (i.e. will produce 4 * width pixels)
"""
blocks = len(data) // 16 # number of blocks in row
ret = (bytearray(), bytearray(), bytearray(), bytearray())
for block_index in range(blocks):
idx = block_index * 16
block = data[idx : idx + 16]
# Decode next 16-byte block.
a0, a1 = struct.unpack_from("<BB", block)
bits = struct.unpack_from("<6B", block, 2)
alphacode1 = bits[2] | (bits[3] << 8) | (bits[4] << 16) | (bits[5] << 24)
alphacode2 = bits[0] | (bits[1] << 8)
color0, color1 = struct.unpack_from("<HH", block, 8)
(code,) = struct.unpack_from("<I", block, 12)
r0, g0, b0 = unpack_565(color0)
r1, g1, b1 = unpack_565(color1)
for j in range(4):
for i in range(4):
# get next control op and generate a pixel
alphacode_index = 3 * (4 * j + i)
if alphacode_index <= 12:
alphacode = (alphacode2 >> alphacode_index) & 0x07
elif alphacode_index == 15:
alphacode = (alphacode2 >> 15) | ((alphacode1 << 1) & 0x06)
else: # alphacode_index >= 18 and alphacode_index <= 45
alphacode = (alphacode1 >> (alphacode_index - 16)) & 0x07
if alphacode == 0:
a = a0
elif alphacode == 1:
a = a1
elif a0 > a1:
a = ((8 - alphacode) * a0 + (alphacode - 1) * a1) // 7
elif alphacode == 6:
a = 0
elif alphacode == 7:
a = 255
else:
a = ((6 - alphacode) * a0 + (alphacode - 1) * a1) // 5
color_code = (code >> 2 * (4 * j + i)) & 0x03
if color_code == 0:
r, g, b = r0, g0, b0
elif color_code == 1:
r, g, b = r1, g1, b1
elif color_code == 2:
r = (2 * r0 + r1) // 3
g = (2 * g0 + g1) // 3
b = (2 * b0 + b1) // 3
elif color_code == 3:
r = (2 * r1 + r0) // 3
g = (2 * g1 + g0) // 3
b = (2 * b1 + b0) // 3
ret[j].extend([r, g, b, a])
return ret
class BLPFormatError(NotImplementedError):
pass
def _accept(prefix: bytes) -> bool:
return prefix[:4] in (b"BLP1", b"BLP2")
class BlpImageFile(ImageFile.ImageFile):
"""
Blizzard Mipmap Format
"""
format = "BLP"
format_description = "Blizzard Mipmap Format"
def _open(self) -> None:
self.magic = self.fp.read(4)
self.fp.seek(5, os.SEEK_CUR)
(self._blp_alpha_depth,) = struct.unpack("<b", self.fp.read(1))
self.fp.seek(2, os.SEEK_CUR)
self._size = struct.unpack("<II", self.fp.read(8))
if self.magic in (b"BLP1", b"BLP2"):
decoder = self.magic.decode()
else:
msg = f"Bad BLP magic {repr(self.magic)}"
raise BLPFormatError(msg)
self._mode = "RGBA" if self._blp_alpha_depth else "RGB"
self.tile = [(decoder, (0, 0) + self.size, 0, (self.mode, 0, 1))]
class _BLPBaseDecoder(ImageFile.PyDecoder):
_pulls_fd = True
def decode(self, buffer: bytes) -> tuple[int, int]:
try:
self._read_blp_header()
self._load()
except struct.error as e:
msg = "Truncated BLP file"
raise OSError(msg) from e
return -1, 0
@abc.abstractmethod
def _load(self) -> None:
pass
def _read_blp_header(self) -> None:
assert self.fd is not None
self.fd.seek(4)
(self._blp_compression,) = struct.unpack("<i", self._safe_read(4))
(self._blp_encoding,) = struct.unpack("<b", self._safe_read(1))
(self._blp_alpha_depth,) = struct.unpack("<b", self._safe_read(1))
(self._blp_alpha_encoding,) = struct.unpack("<b", self._safe_read(1))
self.fd.seek(1, os.SEEK_CUR) # mips
self.size = struct.unpack("<II", self._safe_read(8))
if isinstance(self, BLP1Decoder):
# Only present for BLP1
(self._blp_encoding,) = struct.unpack("<i", self._safe_read(4))
self.fd.seek(4, os.SEEK_CUR) # subtype
self._blp_offsets = struct.unpack("<16I", self._safe_read(16 * 4))
self._blp_lengths = struct.unpack("<16I", self._safe_read(16 * 4))
def _safe_read(self, length: int) -> bytes:
return ImageFile._safe_read(self.fd, length)
def _read_palette(self) -> list[tuple[int, int, int, int]]:
ret = []
for i in range(256):
try:
b, g, r, a = struct.unpack("<4B", self._safe_read(4))
except struct.error:
break
ret.append((b, g, r, a))
return ret
def _read_bgra(self, palette: list[tuple[int, int, int, int]]) -> bytearray:
data = bytearray()
_data = BytesIO(self._safe_read(self._blp_lengths[0]))
while True:
try:
(offset,) = struct.unpack("<B", _data.read(1))
except struct.error:
break
b, g, r, a = palette[offset]
d: tuple[int, ...] = (r, g, b)
if self._blp_alpha_depth:
d += (a,)
data.extend(d)
return data
class BLP1Decoder(_BLPBaseDecoder):
def _load(self) -> None:
if self._blp_compression == Format.JPEG:
self._decode_jpeg_stream()
elif self._blp_compression == 1:
if self._blp_encoding in (4, 5):
palette = self._read_palette()
data = self._read_bgra(palette)
self.set_as_raw(data)
else:
msg = f"Unsupported BLP encoding {repr(self._blp_encoding)}"
raise BLPFormatError(msg)
else:
msg = f"Unsupported BLP compression {repr(self._blp_encoding)}"
raise BLPFormatError(msg)
def _decode_jpeg_stream(self) -> None:
from .JpegImagePlugin import JpegImageFile
(jpeg_header_size,) = struct.unpack("<I", self._safe_read(4))
jpeg_header = self._safe_read(jpeg_header_size)
assert self.fd is not None
self._safe_read(self._blp_offsets[0] - self.fd.tell()) # What IS this?
data = self._safe_read(self._blp_lengths[0])
data = jpeg_header + data
image = JpegImageFile(BytesIO(data))
Image._decompression_bomb_check(image.size)
if image.mode == "CMYK":
decoder_name, extents, offset, args = image.tile[0]
image.tile = [(decoder_name, extents, offset, (args[0], "CMYK"))]
r, g, b = image.convert("RGB").split()
reversed_image = Image.merge("RGB", (b, g, r))
self.set_as_raw(reversed_image.tobytes())
class BLP2Decoder(_BLPBaseDecoder):
def _load(self) -> None:
palette = self._read_palette()
assert self.fd is not None
self.fd.seek(self._blp_offsets[0])
if self._blp_compression == 1:
# Uncompressed or DirectX compression
if self._blp_encoding == Encoding.UNCOMPRESSED:
data = self._read_bgra(palette)
elif self._blp_encoding == Encoding.DXT:
data = bytearray()
if self._blp_alpha_encoding == AlphaEncoding.DXT1:
linesize = (self.size[0] + 3) // 4 * 8
for yb in range((self.size[1] + 3) // 4):
for d in decode_dxt1(
self._safe_read(linesize), alpha=bool(self._blp_alpha_depth)
):
data += d
elif self._blp_alpha_encoding == AlphaEncoding.DXT3:
linesize = (self.size[0] + 3) // 4 * 16
for yb in range((self.size[1] + 3) // 4):
for d in decode_dxt3(self._safe_read(linesize)):
data += d
elif self._blp_alpha_encoding == AlphaEncoding.DXT5:
linesize = (self.size[0] + 3) // 4 * 16
for yb in range((self.size[1] + 3) // 4):
for d in decode_dxt5(self._safe_read(linesize)):
data += d
else:
msg = f"Unsupported alpha encoding {repr(self._blp_alpha_encoding)}"
raise BLPFormatError(msg)
else:
msg = f"Unknown BLP encoding {repr(self._blp_encoding)}"
raise BLPFormatError(msg)
else:
msg = f"Unknown BLP compression {repr(self._blp_compression)}"
raise BLPFormatError(msg)
self.set_as_raw(data)
class BLPEncoder(ImageFile.PyEncoder):
_pushes_fd = True
def _write_palette(self) -> bytes:
data = b""
assert self.im is not None
palette = self.im.getpalette("RGBA", "RGBA")
for i in range(len(palette) // 4):
r, g, b, a = palette[i * 4 : (i + 1) * 4]
data += struct.pack("<4B", b, g, r, a)
while len(data) < 256 * 4:
data += b"\x00" * 4
return data
def encode(self, bufsize: int) -> tuple[int, int, bytes]:
palette_data = self._write_palette()
offset = 20 + 16 * 4 * 2 + len(palette_data)
data = struct.pack("<16I", offset, *((0,) * 15))
assert self.im is not None
w, h = self.im.size
data += struct.pack("<16I", w * h, *((0,) * 15))
data += palette_data
for y in range(h):
for x in range(w):
data += struct.pack("<B", self.im.getpixel((x, y)))
return len(data), 0, data
def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
if im.mode != "P":
msg = "Unsupported BLP image mode"
raise ValueError(msg)
magic = b"BLP1" if im.encoderinfo.get("blp_version") == "BLP1" else b"BLP2"
fp.write(magic)
fp.write(struct.pack("<i", 1)) # Uncompressed or DirectX compression
fp.write(struct.pack("<b", Encoding.UNCOMPRESSED))
fp.write(struct.pack("<b", 1 if im.palette.mode == "RGBA" else 0))
fp.write(struct.pack("<b", 0)) # alpha encoding
fp.write(struct.pack("<b", 0)) # mips
fp.write(struct.pack("<II", *im.size))
if magic == b"BLP1":
fp.write(struct.pack("<i", 5))
fp.write(struct.pack("<i", 0))
ImageFile._save(im, fp, [("BLP", (0, 0) + im.size, 0, im.mode)])
Image.register_open(BlpImageFile.format, BlpImageFile, _accept)
Image.register_extension(BlpImageFile.format, ".blp")
Image.register_decoder("BLP1", BLP1Decoder)
Image.register_decoder("BLP2", BLP2Decoder)
Image.register_save(BlpImageFile.format, _save)
Image.register_encoder("BLP", BLPEncoder)
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