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293 lines
8.4 KiB
Python
293 lines
8.4 KiB
Python
"""
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A Pillow loader for .dds files (S3TC-compressed aka DXTC)
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Jerome Leclanche <jerome@leclan.ch>
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Documentation:
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https://web.archive.org/web/20170802060935/http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt
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The contents of this file are hereby released in the public domain (CC0)
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Full text of the CC0 license:
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https://creativecommons.org/publicdomain/zero/1.0/
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"""
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from __future__ import annotations
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import struct
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from io import BytesIO
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from typing import IO
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from PIL import Image, ImageFile
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# Magic ("DDS ")
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DDS_MAGIC = 0x20534444
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# DDS flags
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DDSD_CAPS = 0x1
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DDSD_HEIGHT = 0x2
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DDSD_WIDTH = 0x4
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DDSD_PITCH = 0x8
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DDSD_PIXELFORMAT = 0x1000
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DDSD_MIPMAPCOUNT = 0x20000
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DDSD_LINEARSIZE = 0x80000
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DDSD_DEPTH = 0x800000
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# DDS caps
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DDSCAPS_COMPLEX = 0x8
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DDSCAPS_TEXTURE = 0x1000
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DDSCAPS_MIPMAP = 0x400000
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DDSCAPS2_CUBEMAP = 0x200
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DDSCAPS2_CUBEMAP_POSITIVEX = 0x400
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DDSCAPS2_CUBEMAP_NEGATIVEX = 0x800
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DDSCAPS2_CUBEMAP_POSITIVEY = 0x1000
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DDSCAPS2_CUBEMAP_NEGATIVEY = 0x2000
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DDSCAPS2_CUBEMAP_POSITIVEZ = 0x4000
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DDSCAPS2_CUBEMAP_NEGATIVEZ = 0x8000
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DDSCAPS2_VOLUME = 0x200000
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# Pixel Format
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DDPF_ALPHAPIXELS = 0x1
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DDPF_ALPHA = 0x2
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DDPF_FOURCC = 0x4
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DDPF_PALETTEINDEXED8 = 0x20
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DDPF_RGB = 0x40
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DDPF_LUMINANCE = 0x20000
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# dds.h
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DDS_FOURCC = DDPF_FOURCC
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DDS_RGB = DDPF_RGB
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DDS_RGBA = DDPF_RGB | DDPF_ALPHAPIXELS
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DDS_LUMINANCE = DDPF_LUMINANCE
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DDS_LUMINANCEA = DDPF_LUMINANCE | DDPF_ALPHAPIXELS
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DDS_ALPHA = DDPF_ALPHA
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DDS_PAL8 = DDPF_PALETTEINDEXED8
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DDS_HEADER_FLAGS_TEXTURE = DDSD_CAPS | DDSD_HEIGHT | DDSD_WIDTH | DDSD_PIXELFORMAT
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DDS_HEADER_FLAGS_MIPMAP = DDSD_MIPMAPCOUNT
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DDS_HEADER_FLAGS_VOLUME = DDSD_DEPTH
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DDS_HEADER_FLAGS_PITCH = DDSD_PITCH
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DDS_HEADER_FLAGS_LINEARSIZE = DDSD_LINEARSIZE
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DDS_HEIGHT = DDSD_HEIGHT
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DDS_WIDTH = DDSD_WIDTH
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DDS_SURFACE_FLAGS_TEXTURE = DDSCAPS_TEXTURE
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DDS_SURFACE_FLAGS_MIPMAP = DDSCAPS_COMPLEX | DDSCAPS_MIPMAP
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DDS_SURFACE_FLAGS_CUBEMAP = DDSCAPS_COMPLEX
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DDS_CUBEMAP_POSITIVEX = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_POSITIVEX
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DDS_CUBEMAP_NEGATIVEX = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_NEGATIVEX
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DDS_CUBEMAP_POSITIVEY = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_POSITIVEY
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DDS_CUBEMAP_NEGATIVEY = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_NEGATIVEY
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DDS_CUBEMAP_POSITIVEZ = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_POSITIVEZ
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DDS_CUBEMAP_NEGATIVEZ = DDSCAPS2_CUBEMAP | DDSCAPS2_CUBEMAP_NEGATIVEZ
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# DXT1
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DXT1_FOURCC = 0x31545844
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# DXT3
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DXT3_FOURCC = 0x33545844
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# DXT5
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DXT5_FOURCC = 0x35545844
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def _decode565(bits: int) -> tuple[int, int, int]:
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a = ((bits >> 11) & 0x1F) << 3
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b = ((bits >> 5) & 0x3F) << 2
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c = (bits & 0x1F) << 3
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return a, b, c
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def _c2a(a: int, b: int) -> int:
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return (2 * a + b) // 3
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def _c2b(a: int, b: int) -> int:
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return (a + b) // 2
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def _c3(a: int, b: int) -> int:
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return (2 * b + a) // 3
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def _dxt1(data: IO[bytes], width: int, height: int) -> bytes:
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# TODO implement this function as pixel format in decode.c
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ret = bytearray(4 * width * height)
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for y in range(0, height, 4):
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for x in range(0, width, 4):
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color0, color1, bits = struct.unpack("<HHI", data.read(8))
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r0, g0, b0 = _decode565(color0)
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r1, g1, b1 = _decode565(color1)
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# Decode this block into 4x4 pixels
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for j in range(4):
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for i in range(4):
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# get next control op and generate a pixel
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control = bits & 3
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bits = bits >> 2
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if control == 0:
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r, g, b = r0, g0, b0
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elif control == 1:
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r, g, b = r1, g1, b1
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elif control == 2:
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if color0 > color1:
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r, g, b = _c2a(r0, r1), _c2a(g0, g1), _c2a(b0, b1)
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else:
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r, g, b = _c2b(r0, r1), _c2b(g0, g1), _c2b(b0, b1)
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elif control == 3:
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if color0 > color1:
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r, g, b = _c3(r0, r1), _c3(g0, g1), _c3(b0, b1)
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else:
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r, g, b = 0, 0, 0
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idx = 4 * ((y + j) * width + x + i)
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ret[idx : idx + 4] = struct.pack("4B", r, g, b, 255)
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return bytes(ret)
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def _dxtc_alpha(a0: int, a1: int, ac0: int, ac1: int, ai: int) -> int:
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if ai <= 12:
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ac = (ac0 >> ai) & 7
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elif ai == 15:
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ac = (ac0 >> 15) | ((ac1 << 1) & 6)
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else:
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ac = (ac1 >> (ai - 16)) & 7
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if ac == 0:
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alpha = a0
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elif ac == 1:
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alpha = a1
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elif a0 > a1:
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alpha = ((8 - ac) * a0 + (ac - 1) * a1) // 7
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elif ac == 6:
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alpha = 0
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elif ac == 7:
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alpha = 0xFF
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else:
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alpha = ((6 - ac) * a0 + (ac - 1) * a1) // 5
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return alpha
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def _dxt5(data: IO[bytes], width: int, height: int) -> bytes:
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# TODO implement this function as pixel format in decode.c
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ret = bytearray(4 * width * height)
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for y in range(0, height, 4):
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for x in range(0, width, 4):
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a0, a1, ac0, ac1, c0, c1, code = struct.unpack("<2BHI2HI", data.read(16))
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r0, g0, b0 = _decode565(c0)
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r1, g1, b1 = _decode565(c1)
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for j in range(4):
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for i in range(4):
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ai = 3 * (4 * j + i)
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alpha = _dxtc_alpha(a0, a1, ac0, ac1, ai)
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cc = (code >> 2 * (4 * j + i)) & 3
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if cc == 0:
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r, g, b = r0, g0, b0
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elif cc == 1:
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r, g, b = r1, g1, b1
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elif cc == 2:
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r, g, b = _c2a(r0, r1), _c2a(g0, g1), _c2a(b0, b1)
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elif cc == 3:
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r, g, b = _c3(r0, r1), _c3(g0, g1), _c3(b0, b1)
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idx = 4 * ((y + j) * width + x + i)
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ret[idx : idx + 4] = struct.pack("4B", r, g, b, alpha)
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return bytes(ret)
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class DdsImageFile(ImageFile.ImageFile):
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format = "DDS"
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format_description = "DirectDraw Surface"
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def _open(self) -> None:
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if not _accept(self.fp.read(4)):
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msg = "not a DDS file"
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raise SyntaxError(msg)
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(header_size,) = struct.unpack("<I", self.fp.read(4))
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if header_size != 124:
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msg = f"Unsupported header size {repr(header_size)}"
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raise OSError(msg)
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header_bytes = self.fp.read(header_size - 4)
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if len(header_bytes) != 120:
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msg = f"Incomplete header: {len(header_bytes)} bytes"
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raise OSError(msg)
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header = BytesIO(header_bytes)
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flags, height, width = struct.unpack("<3I", header.read(12))
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self._size = (width, height)
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self._mode = "RGBA"
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pitch, depth, mipmaps = struct.unpack("<3I", header.read(12))
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struct.unpack("<11I", header.read(44)) # reserved
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# pixel format
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pfsize, pfflags = struct.unpack("<2I", header.read(8))
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fourcc = header.read(4)
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bitcount, rmask, gmask, bmask, amask = struct.unpack("<5I", header.read(20))
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if fourcc == b"DXT1":
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self.decoder = "DXT1"
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elif fourcc == b"DXT5":
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self.decoder = "DXT5"
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else:
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msg = f"Unimplemented pixel format {repr(fourcc)}"
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raise NotImplementedError(msg)
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self.tile = [
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ImageFile._Tile(self.decoder, (0, 0) + self.size, 0, (self.mode, 0, 1))
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]
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def load_seek(self, pos: int) -> None:
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pass
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class DXT1Decoder(ImageFile.PyDecoder):
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_pulls_fd = True
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def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:
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assert self.fd is not None
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try:
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self.set_as_raw(_dxt1(self.fd, self.state.xsize, self.state.ysize))
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except struct.error as e:
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msg = "Truncated DDS file"
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raise OSError(msg) from e
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return -1, 0
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class DXT5Decoder(ImageFile.PyDecoder):
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_pulls_fd = True
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def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:
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assert self.fd is not None
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try:
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self.set_as_raw(_dxt5(self.fd, self.state.xsize, self.state.ysize))
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except struct.error as e:
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msg = "Truncated DDS file"
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raise OSError(msg) from e
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return -1, 0
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Image.register_decoder("DXT1", DXT1Decoder)
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Image.register_decoder("DXT5", DXT5Decoder)
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def _accept(prefix: bytes) -> bool:
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return prefix.startswith(b"DDS ")
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Image.register_open(DdsImageFile.format, DdsImageFile, _accept)
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Image.register_extension(DdsImageFile.format, ".dds")
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