199 lines
6.3 KiB
Python
199 lines
6.3 KiB
Python
"""
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S3TC DXT1/DXT5 Texture Decompression
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Adapted from https://github.com/leamsii/Python-DXT-Decompress to add types
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and take in bytes instead of file pointers. Inspired by Benjamin Dobell.
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Original C++ code https://github.com/Benjamin-Dobell/s3tc-dxt-decompression
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"""
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import io
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import struct
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from typing import List, Optional, Tuple
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def unpack(_bytes: bytes) -> int:
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STRUCT_SIGNS = {
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1: 'B',
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2: 'H',
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4: 'I',
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8: 'Q'
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}
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return struct.unpack('<' + STRUCT_SIGNS[len(_bytes)], _bytes)[0]
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# This function converts RGB565 format to raw pixels
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def unpackRGB(packed: int) -> Tuple[int, int, int, int]:
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R = (packed >> 11) & 0x1F
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G = (packed >> 5) & 0x3F
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B = (packed) & 0x1F
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R = (R << 3) | (R >> 2)
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G = (G << 2) | (G >> 4)
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B = (B << 3) | (B >> 2)
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return (R, G, B, 255)
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class DXTBuffer:
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def __init__(self, width: int, height: int):
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self.width = width
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self.height = height
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self.block_countx = self.width // 4
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self.block_county = self.height // 4
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self.decompressed_buffer: List[Optional[bytes]] = [None] * ((width * height) * 2) # Dont ask me why
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def DXT5Decompress(self, filedata: bytes) -> bytes:
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# Loop through each block and decompress it
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file = io.BytesIO(filedata)
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for row in range(self.block_county):
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for col in range(self.block_countx):
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# Get the alpha values
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a0 = unpack(file.read(1))
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a1 = unpack(file.read(1))
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atable = file.read(6)
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acode0 = atable[2] | (atable[3] << 8) | (atable[4] << 16) | (atable[5] << 24)
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acode1 = atable[0] | (atable[1] << 8)
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# Color 1 color 2, color look up table
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c0 = unpack(file.read(2))
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c1 = unpack(file.read(2))
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ctable = unpack(file.read(4))
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# The 4x4 Lookup table loop
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for j in range(4):
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for i in range(4):
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alpha = self.getAlpha(j, i, a0, a1, acode0, acode1)
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self.getColors(
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row * 4,
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col * 4,
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i,
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j,
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ctable,
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unpackRGB(c0),
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unpackRGB(c1),
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alpha,
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) # Set the color for the current pixel
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return b''.join([x for x in self.decompressed_buffer if x is not None])
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def DXT1Decompress(self, filedata: bytes) -> bytes:
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# Loop through each block and decompress it
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file = io.BytesIO(filedata)
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for row in range(self.block_county):
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for col in range(self.block_countx):
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# Color 1 color 2, color look up table
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c0 = unpack(file.read(2))
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c1 = unpack(file.read(2))
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ctable = unpack(file.read(4))
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# The 4x4 Lookup table loop
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for j in range(4):
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for i in range(4):
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self.getColors(
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row * 4,
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col * 4,
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i,
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j,
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ctable,
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unpackRGB(c0),
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unpackRGB(c1),
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255,
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) # Set the color for the current pixel
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return b''.join([_ for _ in self.decompressed_buffer if _ != 'X'])
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def getColors(
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self,
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x: int,
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y: int,
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i: int,
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j: int,
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ctable: int,
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c0: Tuple[int, int, int, int],
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c1: Tuple[int, int, int, int],
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alpha: int,
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) -> None:
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code = (ctable >> (2 * (4 * i + j))) & 0x03 # Get the color of the current pixel
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pixel_color = None
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r0 = c0[0]
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g0 = c0[1]
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b0 = c0[2]
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r1 = c1[0]
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g1 = c1[1]
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b1 = c1[2]
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# Main two colors
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if code == 0:
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pixel_color = (r0, g0, b0, alpha)
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if code == 1:
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pixel_color = (r1, g1, b1, alpha)
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# Use the lookup table to determine the other two colors
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if c0 > c1:
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if code == 2:
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pixel_color = ((2 * r0 + r1) // 3, (2 * g0 + g1) // 3, (2 * b0 + b1) // 3, alpha)
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if code == 3:
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pixel_color = ((r0 + 2 * r1) // 3, (g0 + 2 * g1) // 3, (b0 + 2 * b1) // 3, alpha)
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else:
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if code == 2:
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pixel_color = ((r0 + r1) // 2, (g0 + g1) // 2, (b0 + b1) // 2, alpha)
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if code == 3:
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pixel_color = (0, 0, 0, alpha)
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# While not surpassing the image dimensions, assign pixels the colors
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if (x + i) < self.width:
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self.decompressed_buffer[(y + j) * self.width + (x + i)] = (
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struct.pack('<B', pixel_color[0]) +
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struct.pack('<B', pixel_color[1]) +
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struct.pack('<B', pixel_color[2]) +
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struct.pack('<B', pixel_color[3])
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)
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def getAlpha(self, i: int, j: int, a0: int, a1: int, acode0: int, acode1: int) -> int:
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# Using the same method as the colors calculate the alpha values
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alpha = 255
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alpha_index = 3 * (4 * j + i)
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alpha_code = None
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if alpha_index <= 12:
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alpha_code = (acode1 >> alpha_index) & 0x07
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elif alpha_index == 15:
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alpha_code = (acode1 >> 15) | ((acode0 << 1) & 0x06)
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else:
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alpha_code = (acode0 >> (alpha_index - 16)) & 0x07
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if alpha_code == 0:
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alpha = a0
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elif alpha_code == 1:
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alpha = a1
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else:
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if a0 > a1:
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alpha = ((8 - alpha_code) * a0 + (alpha_code - 1) * a1) // 7
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else:
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if alpha_code == 6:
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alpha = 0
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elif alpha_code == 7:
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alpha = 255
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elif alpha_code == 5:
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alpha = (1 * a0 + 4 * a1) // 5
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elif alpha_code == 4:
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alpha = (2 * a0 + 3 * a1) // 5
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elif alpha_code == 3:
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alpha = (3 * a0 + 2 * a1) // 5
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elif alpha_code == 2:
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alpha = (4 * a0 + 1 * a1) // 5
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else:
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alpha = 0 # For safety
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return alpha
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