新增: 壁纸切换（主题/本地图片/Bing/纯色渐变）

web/themes/starfield.html

@@ -0,0 +1,64 @@
+<canvas id="canvas" style="position:fixed;top:0;left:0;width:100%;height:100%;z-index:1;"></canvas>
+<script>
+var canvas = document.getElementById('canvas');
+var ctx = canvas.getContext('2d');
+
+function resizeCanvas() {
+  canvas.width = window.innerWidth;
+  canvas.height = window.innerHeight;
+}
+resizeCanvas();
+window.addEventListener('resize', resizeCanvas);
+
+var stars = [];
+for (var i = 0; i < 300; i++) {
+  stars.push({
+    x: (Math.random() - 0.5) * canvas.width,
+    y: (Math.random() - 0.5) * canvas.height,
+    z: Math.random() * canvas.width,
+    pz: 0
+  });
+}
+
+var FPS = 15, lastFrame = 0;
+
+function render(ts) {
+  requestAnimationFrame(render);
+  if (ts - lastFrame < 1000 / FPS) return;
+  lastFrame = ts;
+
+  var w = canvas.width, h = canvas.height;
+  var cx = w / 2, cy = h / 2;
+  ctx.fillStyle = 'rgba(2, 3, 12, 0.25)';
+  ctx.fillRect(0, 0, w, h);
+
+  var speed = 8;
+  for (var i = 0; i < stars.length; i++) {
+    var s = stars[i];
+    s.z -= speed;
+    if (s.z <= 0) {
+      s.x = (Math.random() - 0.5) * w;
+      s.y = (Math.random() - 0.5) * h;
+      s.z = w;
+      s.pz = s.z;
+    }
+    var sx = (s.x / s.z) * w * 0.5 + cx;
+    var sy = (s.y / s.z) * h * 0.5 + cy;
+    var px = (s.x / s.pz) * w * 0.5 + cx;
+    var py = (s.y / s.pz) * h * 0.5 + cy;
+    s.pz = s.z;
+    var r = Math.max(0.5, (1 - s.z / w) * 2.5);
+    ctx.beginPath();
+    ctx.moveTo(px, py);
+    ctx.lineTo(sx, sy);
+    ctx.strokeStyle = 'rgba(200, 220, 255, ' + ((1 - s.z / w) * 0.8) + ')';
+    ctx.lineWidth = r;
+    ctx.stroke();
+    ctx.beginPath();
+    ctx.arc(sx, sy, r * 0.6, 0, Math.PI * 2);
+    ctx.fillStyle = 'rgba(220, 235, 255, ' + ((1 - s.z / w) * 0.9) + ')';
+    ctx.fill();
+  }
+}
+requestAnimationFrame(render);
+</script>