First public commit.

lenser/coco3/convert/mono.py

@@ -0,0 +1,45 @@
+"""CoCo 3 GIME monochrome: 640x192, 2 colours (black + white) -- the highest-
+resolution CoCo 3 mode, tone carried by dithering.  ``--mono-base`` tints the
+second tone."""
+from __future__ import annotations
+
+import numpy as np
+
+from ... import dither, palette as c64pal
+from ...convert.base import Conversion, perceptual_error
+from .. import palette as g
+from . import _common
+
+WIDTH, HEIGHT = 640, 192
+PIXEL_ASPECT = 0.5
+CRES = 0
+
+
+def convert(img_rgb, palette_name="gime", dither_mode="floyd",
+            intensive=False, base_color=None):
+    plab = g.palette_lab()
+    black = min(g.GREYS, key=lambda i: plab[i, 0])
+    if base_color in range(64) and base_color != black:
+        ramp = sorted({black, int(base_color)}, key=lambda i: plab[i, 0])
+    else:
+        ramp = sorted(g.GREYS, key=lambda i: plab[i, 0])
+        ramp = [ramp[0], ramp[-1]]                  # black + white
+
+    img_lab = c64pal.srgb_to_lab(img_rgb)
+    mono_lab = np.zeros_like(img_lab); mono_lab[..., 0] = img_lab[..., 0]
+    plab_mono = np.zeros_like(plab); plab_mono[:, 0] = plab[:, 0]
+    allowed = np.tile(np.array(ramp), (*mono_lab.shape[:2], 1))
+    idx = dither.quantize(mono_lab, allowed, plab_mono, dither_mode).astype(np.int64)
+    lut = {p: k for k, p in enumerate(ramp)}
+    pen = np.vectorize(lut.get)(idx).astype(np.uint8)
+
+    screen = _common.PACK[CRES](pen)
+    prgb = g.get_palette().astype(np.uint8)
+    return Conversion(
+        mode="mono", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx.astype(np.uint16), data=screen, data_addr=0x4000,
+        viewer="coco3", preview_rgb=prgb[idx.astype(np.uint16)],
+        error=perceptual_error(idx, mono_lab, plab_mono),
+        meta={"palette": "gime", "dither": dither_mode, "cres": CRES,
+              "inks": ramp, "border": ramp[0]},
+    )