Solidify unit sprite readability

scripts/solidify-unit-alpha.py

@@ -0,0 +1,67 @@
+from pathlib import Path
+
+from PIL import Image, ImageChops, ImageFilter, ImageStat
+from PIL.PngImagePlugin import PngInfo
+
+
+ROOT = Path(__file__).resolve().parents[1]
+UNIT_DIR = ROOT / "src" / "assets" / "images" / "units"
+PROCESSING_VERSION = "solid-alpha-silhouette-v1"
+
+
+def solid_alpha(value: int) -> int:
+    return 0 if value < 16 else 255
+
+
+def unit_fill_color(image: Image.Image, mask: Image.Image) -> tuple[int, int, int, int]:
+    stat = ImageStat.Stat(image.convert("RGB"), mask=mask)
+    if not stat.count[0]:
+        return (54, 45, 34, 255)
+
+    red, green, blue = stat.mean
+    return (max(30, round(red * 0.45)), max(26, round(green * 0.45)), max(22, round(blue * 0.45)), 255)
+
+
+def solidify_image(image: Image.Image) -> Image.Image:
+    image = image.convert("RGBA")
+    red, green, blue, alpha = image.split()
+    fixed_alpha = alpha.point(solid_alpha)
+    solid = Image.merge("RGBA", (red, green, blue, fixed_alpha))
+    transparent = Image.new("RGBA", image.size, (0, 0, 0, 0))
+    solid = Image.composite(solid, transparent, fixed_alpha)
+
+    silhouette = fixed_alpha.filter(ImageFilter.MaxFilter(15)).filter(ImageFilter.MinFilter(7))
+    silhouette = silhouette.point(lambda value: 255 if value >= 255 else 0)
+    fill_mask = ImageChops.subtract(silhouette, fixed_alpha)
+    fill = Image.new("RGBA", image.size, unit_fill_color(image, fixed_alpha))
+    body = Image.composite(fill, transparent, fill_mask)
+    return Image.alpha_composite(body, solid)
+
+
+def solidify_unit_alpha(path: Path) -> bool:
+    with Image.open(path) as source:
+        if source.info.get("heros_unit_alpha") == PROCESSING_VERSION:
+            return False
+        image = source.convert("RGBA")
+    fixed = solidify_image(image)
+
+    if ImageChops.difference(image, fixed).getbbox() is None:
+        return False
+
+    png_info = PngInfo()
+    png_info.add_text("heros_unit_alpha", PROCESSING_VERSION)
+    fixed.save(path, optimize=True, pnginfo=png_info)
+    return True
+
+
+def main() -> None:
+    changed = 0
+    for path in sorted(UNIT_DIR.glob("unit-*.png")):
+        if solidify_unit_alpha(path):
+            changed += 1
+
+    print(f"Solidified alpha in {changed} unit sprite sheets.")
+
+
+if __name__ == "__main__":
+    main()