mirror of
https://github.com/curioustorvald/Terrarum-sans-bitmap.git
synced 2026-03-07 20:01:52 +09:00
91 lines
2.4 KiB
Python
91 lines
2.4 KiB
Python
"""
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TGA reader for uncompressed true-colour images (Type 2).
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Stores pixels as RGBA8888: (R<<24 | G<<16 | B<<8 | A).
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Matches the convention in TerrarumSansBitmap.kt where .and(255) checks
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the alpha channel (lowest byte).
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"""
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import struct
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from typing import List
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class TgaImage:
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__slots__ = ('width', 'height', 'pixels')
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def __init__(self, width: int, height: int, pixels: List[int]):
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self.width = width
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self.height = height
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self.pixels = pixels # flat array, row-major
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def get_pixel(self, x: int, y: int) -> int:
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"""Get pixel at (x, y) as RGBA8888 (R in bits 31-24, A in bits 7-0)."""
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if x < 0 or x >= self.width or y < 0 or y >= self.height:
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return 0
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return self.pixels[y * self.width + x]
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def read_tga(path: str) -> TgaImage:
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"""Read an uncompressed true-colour TGA file."""
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with open(path, 'rb') as f:
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data = f.read()
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pos = 0
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def u8():
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nonlocal pos
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val = data[pos]
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pos += 1
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return val
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def u16():
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nonlocal pos
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val = struct.unpack_from('<H', data, pos)[0]
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pos += 2
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return val
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id_length = u8()
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colour_map_type = u8()
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image_type = u8()
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# colour map spec (5 bytes)
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u16(); u16(); u8()
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# image spec
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x_origin = u16()
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y_origin = u16()
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width = u16()
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height = u16()
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bits_per_pixel = u8()
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descriptor = u8()
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top_to_bottom = (descriptor & 0x20) != 0
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bytes_per_pixel = bits_per_pixel // 8
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# skip ID
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pos += id_length
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if colour_map_type != 0:
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raise ValueError("Colour-mapped TGA not supported")
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if image_type != 2:
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raise ValueError(f"Only uncompressed true-colour TGA supported (type 2), got type {image_type}")
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if bytes_per_pixel not in (3, 4):
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raise ValueError(f"Only 24-bit or 32-bit TGA supported, got {bits_per_pixel}-bit")
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pixels = [0] * (width * height)
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for row in range(height):
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y = row if top_to_bottom else (height - 1 - row)
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for x in range(width):
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b = data[pos]; pos += 1
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g = data[pos]; pos += 1
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r = data[pos]; pos += 1
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a = data[pos] if bytes_per_pixel == 4 else 0xFF
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if bytes_per_pixel == 4:
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pos += 1
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# Store as RGBA8888: R in high byte, A in low byte
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pixels[y * width + x] = (r << 24) | (g << 16) | (b << 8) | a
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return TgaImage(width, height, pixels)
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