Replace the app icon with an arch bridge

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- **A new app icon.** An off-white arch bridge on black, with three
+  turquoise dots above it. It replaces the bar chart over an arc.
+  `assets/icon.svg` is the source, and `scripts/generate-icon.py` writes the
+  PNG, ICNS and ICO from it.
 ### Added
 - **Simplified Chinese.** Every page, dialog, the menu bar panel, its tray
   menu and the system notifications are translated into 简体中文, and

scripts/generate-icon.py

@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+"""Write every icon format the build uses from assets/icon.svg.
+
+The SVG is the source: a rounded tile, one path for the bridge and a circle
+for each of the dots above it, the bills it carries. This script draws those
+itself, so it needs only Pillow and reads nothing else from the file.
+
+    python3 scripts/generate-icon.py      # run from the repo root
+
+Writes assets/icon.png (1024, on the macOS icon grid with its 100px margin),
+assets/icon.icns, assets/icon.ico (the tile filling the square, 16-256) and
+docs/icon.png (256, the site's favicon).
+"""
+import re
+
+from PIL import Image, ImageChops, ImageDraw
+
+SUPERSAMPLE = 4
+CURVE_STEPS = 48
+
+
+def read_source(path="assets/icon.svg"):
+    text = open(path, encoding="utf-8").read()
+    rect = re.search(r'<rect x="(\d+)" y="(\d+)" width="(\d+)" height="(\d+)" rx="(\d+)" fill="(#\w+)"', text)
+    mark = re.search(r'<path fill="(#\w+)" fill-rule="evenodd" d="([^"]+)"', text)
+    circles = [
+        (float(cx), float(cy), float(r), fill)
+        for cx, cy, r, fill in re.findall(r'<circle cx="([\d.]+)" cy="([\d.]+)" r="([\d.]+)" fill="(#\w+)"', text)
+    ]
+    x, y, w, h, r = (int(v) for v in rect.group(1, 2, 3, 4, 5))
+    return (x, y, x + w, y + h), r, rect.group(6), mark.group(1), mark.group(2), circles
+
+
+def flatten(d):
+    """The subpaths of an absolute M/L/C/Z path, as lists of points."""
+    subpaths, at = [], None
+    for cmd, args in re.findall(r"([MLCZ])([^MLCZ]*)", d):
+        n = [float(v) for v in args.split()]
+        if cmd == "M":
+            at = (n[0], n[1])
+            subpaths.append([at])
+        elif cmd == "L":
+            at = (n[0], n[1])
+            subpaths[-1].append(at)
+        elif cmd == "C":
+            x0, y0 = at
+            for i in range(1, CURVE_STEPS + 1):
+                t = i / CURVE_STEPS
+                u = 1 - t
+                a, b, c, e = u * u * u, 3 * u * u * t, 3 * u * t * t, t * t * t
+                subpaths[-1].append(
+                    (a * x0 + b * n[0] + c * n[2] + e * n[4], a * y0 + b * n[1] + c * n[3] + e * n[5])
+                )
+            at = (n[4], n[5])
+    return subpaths
+
+
+def render(size, source):
+    """The icon at `size` px on the macOS grid, with a transparent margin."""
+    tile, radius, tile_fill, mark_fill, d, circles = source
+    k = size * SUPERSAMPLE / 1024
+    w = round(1024 * k)
+    out = Image.new("RGBA", (w, w), (0, 0, 0, 0))
+    draw = ImageDraw.Draw(out)
+    draw.rounded_rectangle([v * k for v in tile], radius=radius * k, fill=tile_fill)
+    # Even-odd, so that a subpath inside another is a hole.
+    mask = Image.new("1", (w, w), 0)
+    for points in flatten(d):
+        layer = Image.new("1", (w, w), 0)
+        ImageDraw.Draw(layer).polygon([(x * k, y * k) for x, y in points], fill=1)
+        mask = ImageChops.logical_xor(mask, layer)
+    out.paste(mark_fill, (0, 0), mask.convert("L"))
+    for cx, cy, r, fill in circles:
+        draw.ellipse([(cx - r) * k, (cy - r) * k, (cx + r) * k, (cy + r) * k], fill=fill)
+    return out.resize((size, size), Image.LANCZOS)
+
+
+def full_bleed(size, source):
+    """The tile filling the whole square, as Windows icons are drawn."""
+    tile = source[0]
+    big = round(size * 1024 / (tile[2] - tile[0]))
+    m = (big - size) // 2
+    return render(big, source).crop((m, m, m + size, m + size))
+
+
+def main():
+    source = read_source()
+    big = render(1024, source)
+    big.save("assets/icon.png")
+    big.save("assets/icon.icns")
+    render(256, source).save("docs/icon.png")
+    sizes = [16, 24, 32, 48, 64, 128, 256]
+    images = [full_bleed(n, source) for n in sizes]
+    images[-1].save("assets/icon.ico", sizes=[(n, n) for n in sizes], append_images=images[:-1])
+
+
+if __name__ == "__main__":
+    main()