feat(layers): add layer management panel

view/exportArtboardPng.ts

@@ -0,0 +1,72 @@
+import type { Artboard } from "@core/artboard";
+import type { Asset } from "@core/asset";
+import type { Layer } from "@core/layer";
+
+export async function downloadArtboardPng(artboard: Artboard, assets: readonly Asset[]) {
+  const width = Math.max(1, Math.round(artboard.bounds.w));
+  const height = Math.max(1, Math.round(artboard.bounds.h));
+  const canvas = document.createElement("canvas");
+  canvas.width = width;
+  canvas.height = height;
+
+  const context = canvas.getContext("2d");
+  if (!context) throw new Error("Canvas 2D is not available");
+
+  if (artboard.backgroundColor !== "transparent") {
+    context.fillStyle = artboard.backgroundColor;
+    context.fillRect(0, 0, width, height);
+  }
+
+  context.save();
+  context.translate(-artboard.bounds.x, -artboard.bounds.y);
+  for (const layer of artboard.layers) await drawLayer(context, layer, assets);
+  context.restore();
+
+  const url = canvas.toDataURL("image/png");
+  const link = document.createElement("a");
+  link.href = url;
+  link.download = `${safeFilename(artboard.name)}.png`;
+  link.click();
+}
+
+async function drawLayer(context: CanvasRenderingContext2D, layer: Layer, assets: readonly Asset[]) {
+  if (!layer.visible) return;
+
+  context.save();
+  context.globalAlpha *= layer.opacity;
+
+  if (layer.type === "group") {
+    for (const child of layer.children) await drawLayer(context, child, assets);
+    context.restore();
+    return;
+  }
+
+  const asset = assets.find((candidate) => candidate.id === layer.assetId);
+  if (!asset) {
+    context.restore();
+    return;
+  }
+
+  const image = await loadImage(asset.source);
+  context.drawImage(
+    image,
+    layer.transform.position.x,
+    layer.transform.position.y,
+    asset.intrinsicSize.w * layer.transform.scale.x,
+    asset.intrinsicSize.h * layer.transform.scale.y,
+  );
+  context.restore();
+}
+
+function loadImage(source: string) {
+  return new Promise<HTMLImageElement>((resolve, reject) => {
+    const image = new Image();
+    image.onload = () => resolve(image);
+    image.onerror = () => reject(new Error("Failed to load image for export"));
+    image.src = source;
+  });
+}
+
+function safeFilename(name: string) {
+  return name.trim().replace(/[^a-z0-9-_]+/gi, "-").replace(/^-+|-+$/g, "") || "artboard";
+}