First public commit.

lenser/nes/convert/bg.py

@@ -0,0 +1,21 @@
+"""NES background image: 256x240, 4 sub-palettes (universal bg + 3 each), tiles."""
+from __future__ import annotations
+
+from ...convert.base import Conversion
+from . import _common
+
+WIDTH, HEIGHT = 256, 240
+PIXEL_ASPECT = 1.0          # NES pixels are ~square (8:7 really; close enough)
+
+
+def convert(img_rgb, palette_name="nes", dither_mode="floyd",
+            intensive=False, base_color=None):
+    subs = _common.pick_subpalettes(img_rgb, mono=False)
+    pal32, nt, chr_rom, idx, err, plab, prgb = _common.encode(
+        img_rgb, dither_mode, subs)
+    return Conversion(
+        mode="bg", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
+        index_image=idx, data={"palette": pal32, "nametable": nt, "chr": chr_rom},
+        data_addr=0, viewer="nes", preview_rgb=prgb[idx], error=err,
+        meta={"palette": "nes", "dither": dither_mode},
+    )