Working Python version for Commodore.

2026-06-14 17:43:12 -07:00 · 2026-06-14 17:43:12 -07:00 · 2a48f52979
commit 2a48f52979
51 changed files with 3095 additions and 0 deletions
--- a/c64view/convert/multicolor.py
+++ b/c64view/convert/multicolor.py
@ -0,0 +1,80 @@
+"""Multicolor bitmap mode ("Koala"): 160x200, one shared background plus three
+freely chosen colours per 4x8 cell.
+
+Data file layout (PRG, load $2000), matched to viewer/multicolor.s:
+    $2000  bitmap     8000 bytes  (VIC reads here directly)
+    $3F40  screen RAM 1000 bytes  (viewer copies to $0400)
+    $4328  colour RAM 1000 bytes  (viewer copies to $D800)
+    $4710  background  1 byte     (viewer writes to $D021)
+"""
+
+from __future__ import annotations
+
+import numpy as np
+
+from .. import dither, palette as pal
+from . import base
+
+WIDTH, HEIGHT = 160, 200
+CELL_W, CELL_H = 4, 8
+PIXEL_ASPECT = 2.0
+DATA_LOAD = 0x2000
+
+# bit-pair -> colour source:  01 screen hi nibble, 10 screen lo nibble, 11 colour RAM
+_SLOT_BITS = {1: 0b01, 2: 0b10, 3: 0b11}
+
+
+def convert(img_rgb: np.ndarray, palette_name="colodore",
+            dither_mode="bayer", intensive=False) -> base.Conversion:
+    plab = pal.palette_lab(palette_name)
+    img_lab = pal.srgb_to_lab(img_rgb)
+
+    cells, rows, cols = base.cells_lab(img_lab, CELL_W, CELL_H)
+    dist = base.cell_distance(cells, plab)
+
+    if intensive:
+        bg, sets, _ = base.optimize_background(dist, n_free=3)
+    else:
+        bg = base.best_global_color(img_lab, plab)
+        avail = [i for i in range(16) if i != bg]
+        sets, _ = base.select_cell_sets(dist, avail, n_free=3, fixed=(bg,))
+
+    allowed = base.per_pixel_allowed(sets, rows, cols, CELL_W, CELL_H, HEIGHT, WIDTH)
+    index_image = dither.quantize(img_lab, allowed, plab, dither_mode).astype(np.uint8)
+
+    bitmap, screen, colram = _encode(index_image, sets, bg, rows, cols)
+    # This block also *is* a Koala body: bitmap, screen, colram, background.
+    payload = bytes(bitmap) + bytes(screen) + bytes(colram) + bytes([bg])
+
+    conv = base.Conversion(
+        mode="multicolor", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=index_image, data=payload, viewer="multicolor",
+        error=base.mean_error(index_image, img_lab, plab),
+        meta={"palette": palette_name, "dither": dither_mode, "background": bg},
+    )
+    # Standard "Koala Painter" file (load $6000) for use in other C64 art tools.
+    conv.extra_files = [("picture.koa", base.prg(0x6000, payload))]
+    return conv
+
+
+def _encode(index_image, sets, bg, rows, cols):
+    bitmap = np.zeros(8000, dtype=np.uint8)
+    screen = np.zeros(1000, dtype=np.uint8)
+    colram = np.zeros(1000, dtype=np.uint8)
+    for cr in range(rows):
+        for cc in range(cols):
+            ci = cr * cols + cc
+            # sets[ci] = [bg, c1, c2, c3]; assign the three non-bg colours to slots.
+            c1, c2, c3 = int(sets[ci, 1]), int(sets[ci, 2]), int(sets[ci, 3])
+            screen[ci] = ((c1 & 0x0F) << 4) | (c2 & 0x0F)
+            colram[ci] = c3 & 0x0F
+            color_to_bits = {bg: 0b00, c1: 0b01, c2: 0b10, c3: 0b11}
+            base_addr = cr * 320 + cc * 8
+            block = index_image[cr * 8:cr * 8 + 8, cc * 4:cc * 4 + 4]
+            for r in range(8):
+                row = block[r]
+                byte = 0
+                for x in range(4):
+                    byte = (byte << 2) | color_to_bits.get(int(row[x]), 0b00)
+                bitmap[base_addr + r] = byte
+    return bitmap, screen, colram