| |
| from __future__ import annotations |
|
|
| import random |
| import struct |
| import zlib |
| from pathlib import Path |
|
|
|
|
| def main() -> None: |
| out = Path("static/assets/parchment.png") |
| out.parent.mkdir(parents=True, exist_ok=True) |
| write_png(out, 1280, 760) |
| print(f"wrote {out}") |
|
|
|
|
| def write_png(path: Path, width: int, height: int) -> None: |
| random.seed(47) |
| rows = [] |
| for y in range(height): |
| row = bytearray([0]) |
| for x in range(width): |
| dx = abs(x / width - 0.5) |
| dy = abs(y / height - 0.5) |
| vignette = int((dx + dy) * 58) |
| grain = random.randint(-12, 12) |
| wave = int(8 * random.random() + 6 * ((x * y) % 17 == 0)) |
| r = clamp(217 - vignette + grain + wave) |
| g = clamp(190 - vignette + grain) |
| b = clamp(137 - vignette + grain // 2) |
| row.extend([r, g, b, 255]) |
| rows.append(bytes(row)) |
| raw = b"".join(rows) |
| png = b"\x89PNG\r\n\x1a\n" |
| png += chunk(b"IHDR", struct.pack(">IIBBBBB", width, height, 8, 6, 0, 0, 0)) |
| png += chunk(b"IDAT", zlib.compress(raw, 9)) |
| png += chunk(b"IEND", b"") |
| path.write_bytes(png) |
|
|
|
|
| def chunk(kind: bytes, data: bytes) -> bytes: |
| return struct.pack(">I", len(data)) + kind + data + struct.pack(">I", zlib.crc32(kind + data) & 0xFFFFFFFF) |
|
|
|
|
| def clamp(value: int) -> int: |
| return max(0, min(255, value)) |
|
|
|
|
| if __name__ == "__main__": |
| main() |
|
|
