First public commit.

lenser/amiga/palette.py

@@ -0,0 +1,30 @@
+"""Commodore Amiga (OCS/ECS) colour palette.
+
+12-bit colour: 4 bits per channel (x17 -> 0..255), 4096 colours.  A colour
+register value is %0000 RRRR GGGG BBBB.  We index the master palette by the
+packed 12-bit key (R<<8)|(G<<4)|B, which is also the register word.
+"""
+from __future__ import annotations
+
+import numpy as np
+
+from ..palette import srgb_to_lab
+
+_r = (np.arange(4096) >> 8) & 0xF
+_g = (np.arange(4096) >> 4) & 0xF
+_b = np.arange(4096) & 0xF
+PALETTE = (np.stack([_r, _g, _b], axis=1) * 17).astype(np.float64)   # 4096 x 3
+
+GREYS = [(v << 8) | (v << 4) | v for v in range(16)]    # 16 grey keys
+
+
+def color_word(key: int) -> int:
+    return key & 0x0FFF
+
+
+def get_palette() -> np.ndarray:
+    return PALETTE
+
+
+def palette_lab() -> np.ndarray:
+    return srgb_to_lab(PALETTE)