修复了一点bug，然后增加了图层拆分更多的功能

tests/seedream-layer-compose.test.ts

@@ -16,12 +16,16 @@ describe("Seedream layer composition download", () => {
     });
     const close = vi.fn();
     const drawImage = vi.fn();
+    const save = vi.fn();
+    const translate = vi.fn();
+    const rotate = vi.fn();
+    const restore = vi.fn();
     const click = vi.fn();
     const anchor = { href: "", download: "", click, remove: vi.fn() };
     const canvas = {
       width: 0,
       height: 0,
-      getContext: () => ({ clearRect: vi.fn(), drawImage }),
+      getContext: () => ({ clearRect: vi.fn(), drawImage, save, translate, rotate, restore }),
       toBlob: (callback: BlobCallback) => callback(new Blob(["png"], { type: "image/png" }))
     };
 
@@ -35,7 +39,7 @@ describe("Seedream layer composition download", () => {
     vi.stubGlobal("URL", { createObjectURL: () => "blob:composition", revokeObjectURL: vi.fn() });
 
     await expect(downloadSeedreamLayerComposition({
-      items: [{ url: "/api/assets/private-layer/download?inline=1", visible: true, box: [0, 0, 1000, 1000] }],
+      items: [{ url: "/api/assets/private-layer/download?inline=1", visible: true, box: [0, 0, 1000, 1000], rotation: 90 }],
       width: 100,
       height: 100,
       fileName: "composition.png"
@@ -43,6 +47,10 @@ describe("Seedream layer composition download", () => {
 
     expect(fetchMock).toHaveBeenCalledWith("/api/assets/private-layer/download", { credentials: "same-origin" });
     expect(drawImage).toHaveBeenCalledOnce();
+    expect(save).toHaveBeenCalledOnce();
+    expect(translate).toHaveBeenCalledWith(50, 50);
+    expect(rotate).toHaveBeenCalledWith(Math.PI / 2);
+    expect(restore).toHaveBeenCalledOnce();
     expect(click).toHaveBeenCalledOnce();
     expect(close).toHaveBeenCalledOnce();
   });