First public commit.

lenser/ti99/convert/mono.py

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+"""TI-99/4A (TMS9918A) monochrome / tinted-mono mode.
+
+Same 256x192, 2-colours-per-cell format as gm2, but matched by *luminance* to a
+grey ramp (black -> grey -> white) so every cell is neutral -- no colour clash,
+maximum perceived detail, a clean greyscale photo.  Pick a base colour for a
+tinted monochrome instead.  Reuses the gm2 byte packing and viewer.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+from ... import palette as c64pal
+from ...convert import base
+from .. import palette as tpal
+from . import gm2
+
+WIDTH, HEIGHT = gm2.WIDTH, gm2.HEIGHT
+CELL_W, CELL_H = gm2.CELL_W, gm2.CELL_H
+PIXEL_ASPECT = gm2.PIXEL_ASPECT
+
+# Neutral ramp: black(1), grey(14), white(15).  Lighter siblings for tinting.
+NEUTRAL = [1, 14, 15]
+SIBLINGS = {2: 3, 3: 2, 4: 5, 5: 4, 6: 9, 8: 9, 9: 8, 12: 14, 13: 9}
+
+
+def convert(img_rgb, palette_name="tms9918", dither_mode="atkinson",
+            intensive=False, base_color=None):
+    plab = tpal.palette_lab()
+    prgb = tpal.get_palette().astype(np.uint8)
+    ramp = base.luminance_ramp(plab, NEUTRAL, base_color, SIBLINGS)
+
+    idx, sets, rows, cols, err = base.mono_render(
+        img_rgb, plab, ramp, WIDTH, HEIGHT, CELL_W, CELL_H, dither_mode, n_free=2)
+
+    pattern, colors = gm2._encode(idx, sets, rows, cols)
+    data = bytes(pattern) + bytes(colors)
+
+    return base.Conversion(
+        mode="mono", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx.astype(np.uint16), data=data, data_addr=0,
+        viewer="gm2", preview_rgb=prgb[idx], error=err,
+        meta={"palette": "tms9918", "dither": dither_mode, "base_color": base_color},
+    )