Add two-stage charged-crystal demo and original art set.

tools/punch_render_alpha.py

@@ -0,0 +1,72 @@
+"""Knock a flat charcoal field out of generated renders so they can be sprites."""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+from PIL import Image
+
+
+def sample_background(image: Image.Image) -> tuple[float, float, float]:
+    pixels = image.load()
+    width, height = image.size
+    samples: list[tuple[int, int, int]] = []
+    for x, y in (
+        (2, 2),
+        (width - 3, 2),
+        (2, height - 3),
+        (width - 3, height - 3),
+        (width // 2, 2),
+        (width // 2, height - 3),
+    ):
+        pixel = pixels[x, y]
+        samples.append((pixel[0], pixel[1], pixel[2]))
+    count = float(len(samples))
+    return (
+        sum(sample[0] for sample in samples) / count,
+        sum(sample[1] for sample in samples) / count,
+        sum(sample[2] for sample in samples) / count,
+    )
+
+
+def punch(path: Path) -> None:
+    image = Image.open(path).convert("RGBA")
+    background = sample_background(image)
+    pixels = image.load()
+    width, height = image.size
+    for y in range(height):
+        for x in range(width):
+            red, green, blue, _alpha = pixels[x, y]
+            distance = (
+                (red - background[0]) ** 2
+                + (green - background[1]) ** 2
+                + (blue - background[2]) ** 2
+            ) ** 0.5
+            if distance < 18:
+                alpha = 0
+            elif distance < 34:
+                alpha = int((distance - 18) * (255.0 / 16.0))
+            else:
+                alpha = 255
+            pixels[x, y] = (red, green, blue, alpha)
+    image.save(path)
+
+
+def main() -> int:
+    roots = [
+        Path("assets/generated/renders/machines"),
+        Path("assets/generated/renders/logistics"),
+        Path("assets/generated/renders/items"),
+    ]
+    count = 0
+    for root in roots:
+        for path in sorted(root.glob("*.png")):
+            punch(path)
+            count += 1
+    print("PUNCHED %d" % count)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())