First public commit.

lenser/coco3/palette.py

@@ -0,0 +1,34 @@
+"""Tandy CoCo 3 GIME RGB palette.
+
+The GIME produces 64 colours: a 6-bit palette value, bits ``R1 G1 B1 R0 G0 B0``,
+so each of R/G/B is a 2-bit level (x0x55 -> 0, 0x55, 0xAA, 0xFF).  RGB is computed
+exactly as MAME's gime_device::get_rgb_color, so the encoder matches the emulator.
+A palette register ($FFB0-$FFBF) holds this 6-bit value, so the colour index IS
+the byte written to hardware.
+"""
+from __future__ import annotations
+
+import numpy as np
+
+from ..palette import srgb_to_lab
+
+
+def _rgb(c: int):
+    r = (((c >> 4) & 2) | ((c >> 2) & 1)) * 0x55
+    g = (((c >> 3) & 2) | ((c >> 1) & 1)) * 0x55
+    b = (((c >> 2) & 2) | ((c >> 0) & 1)) * 0x55
+    return (r, g, b)
+
+
+PALETTE = np.array([_rgb(c) for c in range(64)], dtype=np.float64)
+
+# Neutral grey ramp (R==G==B): 6-bit values 0, 7, 56, 63.
+GREYS = [c for c in range(64) if PALETTE[c, 0] == PALETTE[c, 1] == PALETTE[c, 2]]
+
+
+def get_palette() -> np.ndarray:
+    return PALETTE
+
+
+def palette_lab() -> np.ndarray:
+    return srgb_to_lab(PALETTE)