First public commit.

lenser/coco/convert/__init__.py

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+"""TRS-80 Color Computer conversion dispatch."""
+from __future__ import annotations
+from ... import imageprep
+from . import pmode3, pmode4, mono
+
+_MODULES = {"pmode4": pmode4, "pmode3": pmode3, "mono": mono}
+MODES = list(_MODULES.keys())
+
+
+def convert_image(path_or_img, mode="pmode4", palette_name="mc6847",
+                  dither_mode="floyd", intensive=False, prep_opt=None, base_color=None):
+    prep_opt = prep_opt or imageprep.PrepOptions()
+    module = _MODULES[mode]
+    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/coco/convert/mono.py

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+"""CoCo monochrome -- PMODE 4's 256x192 black & white, exposed as the standard
+``mono`` mode for cross-platform parity (tone carried by dithering)."""
+from __future__ import annotations
+
+from . import pmode4
+
+WIDTH, HEIGHT, PIXEL_ASPECT = pmode4.WIDTH, pmode4.HEIGHT, pmode4.PIXEL_ASPECT
+
+
+def convert(img_rgb, palette_name="mc6847", dither_mode="floyd",
+            intensive=False, base_color=None):
+    conv = pmode4.convert(img_rgb, palette_name, dither_mode, intensive,
+                          base_color=base_color)
+    conv.mode = "mono"
+    return conv

lenser/coco/convert/pmode3.py

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+"""CoCo PMODE 3: 128x192, 4 colours from one MC6847 colour set.
+
+128 wide on a 4:3 screen -> 2:1 pixels (like C64 multicolor).  The 4 colours are
+fixed per CSS set (green/yellow/blue/red or buff/cyan/magenta/orange); we dither
+to whichever set reproduces the image with lower error and tell the viewer which.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+from ... import dither
+from ...convert.base import Conversion, perceptual_error
+from ...palette import srgb_to_lab
+from .. import palette as cpal
+
+WIDTH, HEIGHT = 128, 192
+PIXEL_ASPECT = 2.0
+
+
+def convert(img_rgb, palette_name="mc6847", dither_mode="floyd",
+            intensive=False, base_color=None):
+    img_lab = srgb_to_lab(img_rgb)
+    allowed = np.tile(np.array([0, 1, 2, 3]), (HEIGHT, WIDTH, 1))
+
+    best = None
+    for vdg, rgb in cpal.PMODE3_SETS.items():
+        plab = srgb_to_lab(rgb)
+        idx = dither.quantize(img_lab, allowed, plab, dither_mode).astype(np.uint8)
+        err = perceptual_error(idx, img_lab, plab)
+        if best is None or err < best[0]:
+            best = (err, vdg, rgb, plab, idx)
+
+    err, vdg, rgb, plab, idx = best
+    data = cpal.pack_pmode3(idx)                 # 6144-byte video buffer
+    preview = rgb.astype(np.uint8)[idx]
+
+    return Conversion(
+        mode="pmode3", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx.astype(np.uint16), data=data, data_addr=0,
+        viewer="pmode3", preview_rgb=preview,
+        error=err,
+        meta={"palette": "mc6847", "dither": dither_mode, "vdg": vdg},
+    )

lenser/coco/convert/pmode4.py

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+"""CoCo PMODE 4: 256x192, 1 bit/pixel, black & white (buff on black).
+
+The CoCo's high-resolution monochrome mode -- 256x192 is exactly 4:3, so square
+pixels.  Tone is carried by dithering, like Apple HGR mono.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+from ... import dither
+from ...convert.base import Conversion, perceptual_error
+from .. import palette as cpal
+
+WIDTH, HEIGHT = 256, 192
+PIXEL_ASPECT = 1.0
+
+
+def convert(img_rgb, palette_name="mc6847", dither_mode="floyd",
+            intensive=False, base_color=None):
+    from ...palette import srgb_to_lab
+    plab = cpal.mono_lab()
+    L = srgb_to_lab(img_rgb)[..., 0]
+    img_mono = np.zeros((HEIGHT, WIDTH, 3))
+    img_mono[..., 0] = L
+    plab_mono = np.zeros((2, 3))
+    plab_mono[:, 0] = plab[:, 0]
+
+    allowed = np.tile(np.array([0, 1]), (HEIGHT, WIDTH, 1))
+    idx = dither.quantize(img_mono, allowed, plab_mono, dither_mode).astype(np.uint8)
+
+    data = cpal.pack_pmode4(idx)                 # 6144-byte video buffer
+    preview = cpal.MONO.astype(np.uint8)[idx]
+
+    return Conversion(
+        mode="pmode4", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx.astype(np.uint16), data=data, data_addr=0,
+        viewer="pmode4", preview_rgb=preview,
+        error=perceptual_error(idx, img_mono, plab_mono),
+        meta={"palette": "mc6847", "dither": dither_mode, "vdg": 0xF8},
+    )