First public commit.

lenser/atari/convert/mono.py

@@ -0,0 +1,16 @@
+"""Atari monochrome -- GR.9's 16 luminance shades, exposed as the standard
+``mono`` mode for cross-platform parity.  Greyscale by default; ``--mono-base``
+tints it to one of the GTIA hues (16 real shades of that hue)."""
+from __future__ import annotations
+
+from . import gr9
+
+WIDTH, HEIGHT, PIXEL_ASPECT = gr9.WIDTH, gr9.HEIGHT, gr9.PIXEL_ASPECT
+
+
+def convert(img_rgb, palette_name="ntsc", dither_mode="floyd",
+            intensive=False, base_color=None):
+    conv = gr9.convert(img_rgb, palette_name, dither_mode, intensive,
+                       base_color=base_color)
+    conv.mode = "mono"
+    return conv