First public commit.

lenser/a5200/convert/__init__.py

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+"""Atari 5200 conversion dispatch.
+
+The 5200 has the same ANTIC + GTIA graphics hardware (and the same 256-colour GTIA
+palette) as the Atari 400/800, so it reuses the Atari 8-bit encoders unchanged.
+GR.9 doubles as the monochrome / tinted-mono mode (16 real luminance shades of one
+hue).  GR.15+DLI is omitted: per-scanline DLI colour changes need OS NMI vectoring
+the 5200 lacks.
+"""
+from __future__ import annotations
+
+from ...atari.convert import convert_image as _atari_convert
+
+MODES = ["gr15", "gr9", "gr8", "mono"]
+
+
+def convert_image(path_or_img, mode="gr15", palette_name="ntsc",
+                  dither_mode="floyd", intensive=False, prep_opt=None,
+                  base_color=None):
+    if mode not in MODES:
+        mode = "gr15"
+    return _atari_convert(path_or_img, mode=mode, palette_name="ntsc",
+                          dither_mode=dither_mode, intensive=intensive,
+                          prep_opt=prep_opt, base_color=base_color)