First public commit.

lenser/sms/palette.py

@@ -0,0 +1,33 @@
+"""Sega Master System VDP (315-5124) palette.
+
+The SMS palette is 64 colours: each CRAM byte is %00BBGGRR -- 2 bits per channel
+(x85 -> 0,85,170,255).  The colour index IS the byte written to CRAM, so PALETTE
+is indexed by hardware value 0-63.  Two 16-colour palettes (background + sprite)
+are loaded; an image uses up to 32 colours on screen.
+"""
+from __future__ import annotations
+
+import numpy as np
+
+from ..palette import srgb_to_lab
+
+
+def _rgb(c):
+    r = (c & 3) * 85
+    g = ((c >> 2) & 3) * 85
+    b = ((c >> 4) & 3) * 85
+    return (r, g, b)
+
+
+PALETTE = np.array([_rgb(c) for c in range(64)], dtype=np.float64)
+
+# greys: R==G==B -> byte where the three 2-bit fields are equal (0,21,42,63).
+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)