fix(POSTV1-editor): 修复多选拖动与底图调整

tests/unit/wp4-01-editor-canvas.test.ts

@@ -1,8 +1,11 @@
 import { describe, expect, it } from "vitest";
 
 import {
+  adjustBackgroundPixels,
+  backgroundDrawPlan,
   CanvasEditHistory,
   createEditorCanvasState,
+  cssFilterForBackground,
   defaultBackgroundAdjustments,
   deserializeFabricCanvas,
   switchBackground,
@@ -24,6 +27,35 @@ const element = {
 };
 
 describe("TDD-WP4-BG-001/002 canvas boundary", () => {
+  it("builds valid filters and distinct contain/crop draw plans", () => {
+    const adjustments = { ...defaultBackgroundAdjustments(), brightness: 25, contrast: 15, saturation: -20 };
+    expect(cssFilterForBackground(adjustments)).toBe("brightness(125%) contrast(115%) saturate(80%)");
+    expect(cssFilterForBackground(defaultBackgroundAdjustments())).toBe("none");
+
+    expect(backgroundDrawPlan({ height: 200, width: 400 }, { height: 100, width: 100 }, { ...adjustments, fit: "fit" })).toEqual({
+      destination: { height: 50, width: 100, x: 0, y: 25 },
+      source: { height: 200, width: 400, x: 0, y: 0 },
+    });
+    expect(backgroundDrawPlan({ height: 200, width: 400 }, { height: 100, width: 100 }, { ...adjustments, fit: "crop" })).toEqual({
+      destination: { height: 100, width: 100, x: 0, y: 0 },
+      source: { height: 200, width: 200, x: 100, y: 0 },
+    });
+  });
+
+  it("changes pixels for temperature and sharpness without changing alpha", () => {
+    const flat = new Uint8ClampedArray([100, 100, 100, 255]);
+    expect([...adjustBackgroundPixels(flat, 1, 1, { sharpness: 0, temperature: 100 })]).toEqual([135, 108, 65, 255]);
+
+    const edged = new Uint8ClampedArray([
+      100, 100, 100, 255, 100, 100, 100, 255, 100, 100, 100, 255,
+      100, 100, 100, 255, 180, 180, 180, 255, 100, 100, 100, 255,
+      100, 100, 100, 255, 100, 100, 100, 255, 100, 100, 100, 255,
+    ]);
+    const sharpened = adjustBackgroundPixels(edged, 3, 3, { sharpness: 100, temperature: 0 });
+    expect(sharpened[16]).toBe(255);
+    expect(sharpened[19]).toBe(255);
+  });
+
   it("switches background without moving overlays, resets processing, and re-extracts palette", () => {
     const initial = createEditorCanvasState({ assetId: "00000000-0000-4000-8000-000000000010", ratio: "3:4" });
     const withOverlay = { ...initial, background: { ...initial.background, adjustments: { ...initial.background.adjustments, brightness: 42, filter: "mono" } }, elements: [element] };