feat: 添加图层缩略图生成时对遮罩对象的支持，优化图层对象的z-index处理

src/component/Canvas/CanvasEditor/commands/RasterizeLayerCommand.js

@@ -228,6 +228,18 @@ export class RasterizeLayerCommand extends Command {
     const objectsWithZIndex = [];
 
     this.layersToRasterize.forEach((layer) => {
+      if (layer.fill) {
+        const { object } = findObjectById(this.canvas, layer.fill.id);
+        if (object) {
+          // 获取对象在画布中的z-index（数组索引）
+          const zIndex = allCanvasObjects.indexOf(object);
+          objectsWithZIndex.push({
+            object: object,
+            zIndex: zIndex,
+            layerObj: layer.fill,
+          });
+        }
+      }
       if (layer.fabricObjects && layer.fabricObjects.length > 0) {
         layer.fabricObjects.forEach((layerObj) => {
           if (layerObj && layerObj.id) {
@@ -459,11 +471,27 @@ export class ExportLayerToImageCommand extends Command {
       this.canvas.discardActiveObject();
       this.canvas.renderAll();
 
+      // 重新创建遮罩对象
+      let clippingMaskFabricObject = null;
+      if (this.layer?.clippingMask) {
+        // 重新创建遮罩对象
+        clippingMaskFabricObject = await restoreFabricObject(this.layer?.clippingMask, this.canvas);
+
+        clippingMaskFabricObject.clipPath = null;
+        clippingMaskFabricObject.set({
+          absolutePositioned: true,
+        });
+
+        clippingMaskFabricObject.dirty = true;
+        clippingMaskFabricObject.setCoords();
+      }
+
       // 创建图像
       const imageBase64 = await createRasterizedImage({
         canvas: this.canvas,
         fabricObjects: this.objectsToRasterize,
         isReturenDataURL: true,
+        maskObject: clippingMaskFabricObject || null, // 不处理遮罩
       });
 
       // 模拟浏览器下载
@@ -504,6 +532,18 @@ export class ExportLayerToImageCommand extends Command {
     const objectsWithZIndex = [];
 
     this.layersToRasterize.forEach((layer) => {
+      if (layer.fill) {
+        const { object } = findObjectById(this.canvas, layer.fill.id);
+        if (object) {
+          // 获取对象在画布中的z-index（数组索引）
+          const zIndex = allCanvasObjects.indexOf(object);
+          objectsWithZIndex.push({
+            object: object,
+            zIndex: zIndex,
+            layerObj: layer.fill,
+          });
+        }
+      }
       if (layer.fabricObjects && layer.fabricObjects.length > 0) {
         layer.fabricObjects.forEach((layerObj) => {
           if (layerObj && layerObj.id) {