First public commit.

lenser/coco3/convert/__init__.py

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+"""Tandy CoCo 3 (GIME) conversion dispatch."""
+from __future__ import annotations
+
+from ... import imageprep
+from . import gr16, gr4, mono
+
+_MODULES = {"gr16": gr16, "gr4": gr4, "mono": mono}
+MODES = list(_MODULES.keys())
+
+
+def convert_image(path_or_img, mode="gr16", palette_name="gime",
+                  dither_mode="floyd", intensive=False, prep_opt=None,
+                  base_color=None):
+    prep_opt = prep_opt or imageprep.PrepOptions()
+    module = _MODULES.get(mode, gr16)
+    img_rgb = imageprep.prepare(path_or_img, module.WIDTH, module.HEIGHT,
+                                module.PIXEL_ASPECT, prep_opt, border_rgb=(0, 0, 0))
+    return module.convert(img_rgb, palette_name, dither_mode, intensive,
+                          base_color=base_color)

lenser/coco3/convert/_common.py

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+"""Shared CoCo 3 GIME encoder helpers: global palette selection + linear packing.
+
+GIME native graphics modes have no per-cell colour limit: a flat palette of pens
+(16/4/2), each pen any of the 64 colours.  Pick the best N-colour sub-palette,
+dither to it, then pack pens into the LINEAR 80-byte x 192-row screen.
+"""
+from __future__ import annotations
+
+import numpy as np
+
+from ... import dither, palette as c64pal
+from .. import palette as g
+
+BYTES_PER_ROW, ROWS = 80, 192
+
+
+def choose_inks(img_lab, plab, n):
+    """Greedy forward selection of the ``n`` palette colours (0-63) minimising
+    nearest-colour error over the image."""
+    flat = img_lab.reshape(-1, 3)
+    d = np.sum((flat[:, None, :] - plab[None, :, :]) ** 2, axis=-1)
+    chosen, best = [], np.full(flat.shape[0], np.inf)
+    for _ in range(n):
+        cand = np.minimum(best[:, None], d).sum(0)
+        for c in chosen:
+            cand[c] = np.inf
+        c = int(cand.argmin())
+        chosen.append(c)
+        best = np.minimum(best, d[:, c])
+    return sorted(chosen)
+
+
+def render(img_rgb, n, dither_mode, ramp=None):
+    """Return (pen (H,W) 0..n-1, inks (n 6-bit colours), idx (H,W) palette
+    indices, img_lab, plab, prgb)."""
+    plab = g.palette_lab()
+    prgb = g.get_palette().astype(np.uint8)
+    img_lab = c64pal.srgb_to_lab(img_rgb)
+
+    pal_idx = list(ramp) if ramp is not None else choose_inks(img_lab, plab, n)
+    allowed = np.tile(np.array(pal_idx), (*img_lab.shape[:2], 1))
+    idx = dither.quantize(img_lab, allowed, plab, dither_mode).astype(np.int64)
+    lut = {p: k for k, p in enumerate(pal_idx)}
+    pen = np.vectorize(lut.get)(idx).astype(np.uint8)
+    return pen, list(pal_idx), idx.astype(np.uint16), img_lab, plab, prgb
+
+
+def _pack_16(pen):
+    """160x192 pens (0-15) -> 15360 bytes.  2 px/byte, high nibble = left."""
+    scr = bytearray(BYTES_PER_ROW * ROWS)
+    for y in range(ROWS):
+        row = pen[y]
+        base = y * BYTES_PER_ROW
+        for bx in range(BYTES_PER_ROW):
+            scr[base + bx] = (int(row[bx * 2]) << 4) | (int(row[bx * 2 + 1]) & 0x0F)
+    return bytes(scr)
+
+
+def _pack_4(pen):
+    """320x192 pens (0-3) -> 15360 bytes.  4 px/byte, MSB = left."""
+    scr = bytearray(BYTES_PER_ROW * ROWS)
+    for y in range(ROWS):
+        row = pen[y]
+        base = y * BYTES_PER_ROW
+        for bx in range(BYTES_PER_ROW):
+            scr[base + bx] = ((int(row[bx * 4]) << 6) | (int(row[bx * 4 + 1]) << 4) |
+                              (int(row[bx * 4 + 2]) << 2) | int(row[bx * 4 + 3]))
+    return bytes(scr)
+
+
+def _pack_2(pen):
+    """640x192 pens (0-1) -> 15360 bytes.  8 px/byte, MSB = left."""
+    scr = bytearray(BYTES_PER_ROW * ROWS)
+    for y in range(ROWS):
+        row = pen[y]
+        base = y * BYTES_PER_ROW
+        for bx in range(BYTES_PER_ROW):
+            byte = 0
+            for k in range(8):
+                byte |= (int(row[bx * 8 + k]) & 1) << (7 - k)
+            scr[base + bx] = byte
+    return bytes(scr)
+
+
+PACK = {0: _pack_2, 1: _pack_4, 2: _pack_16}    # keyed by CRES

lenser/coco3/convert/gr16.py

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+"""CoCo 3 GIME 160x192, 16 colours from the 64-colour palette (flagship photo
+mode -- wide pixels but the most colour)."""
+from __future__ import annotations
+
+from ...convert.base import Conversion, perceptual_error
+from . import _common
+
+WIDTH, HEIGHT = 160, 192
+PIXEL_ASPECT = 2.0          # 160 wide on a 4:3 screen -> pixels twice as wide
+NCOL = 16
+CRES = 2
+
+
+def convert(img_rgb, palette_name="gime", dither_mode="floyd",
+            intensive=False, base_color=None):
+    pen, inks, idx, img_lab, plab, prgb = _common.render(img_rgb, NCOL, dither_mode)
+    screen = _common.PACK[CRES](pen)
+    return Conversion(
+        mode="gr16", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx, data=screen, data_addr=0x4000, viewer="coco3",
+        preview_rgb=prgb[idx], error=perceptual_error(idx, img_lab, plab),
+        meta={"palette": "gime", "dither": dither_mode, "cres": CRES,
+              "inks": inks, "border": inks[0] if inks else 0},
+    )

lenser/coco3/convert/gr4.py

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+"""CoCo 3 GIME 320x192, 4 colours from the 64-colour palette (more resolution,
+fewer colours than gr16)."""
+from __future__ import annotations
+
+from ...convert.base import Conversion, perceptual_error
+from . import _common
+
+WIDTH, HEIGHT = 320, 192
+PIXEL_ASPECT = 1.0
+NCOL = 4
+CRES = 1
+
+
+def convert(img_rgb, palette_name="gime", dither_mode="floyd",
+            intensive=False, base_color=None):
+    pen, inks, idx, img_lab, plab, prgb = _common.render(img_rgb, NCOL, dither_mode)
+    screen = _common.PACK[CRES](pen)
+    return Conversion(
+        mode="gr4", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx, data=screen, data_addr=0x4000, viewer="coco3",
+        preview_rgb=prgb[idx], error=perceptual_error(idx, img_lab, plab),
+        meta={"palette": "gime", "dither": dither_mode, "cres": CRES,
+              "inks": inks, "border": inks[0] if inks else 0},
+    )

lenser/coco3/convert/mono.py

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+"""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]},
+    )