feat:图片默认下层

src/views/components/Graphics.vue

@@ -1143,6 +1143,7 @@ const dragStart = async (event: DragEvent | MouseEvent|TouchEvent, item: any) =>
       name,
       width,
       height,
+      isBottom:true,
       image: item.image,
       imageRatio: true,
       ratio: true,