feat: 画布图片按原始比例 1:1 显示

- 图片使用 object-contain 保持原始比例，不再裁剪
- 添加 getImageDimensions 函数获取图片原始尺寸
- 图片节点大小根据原始尺寸动态设置（最大 500px，最小 150px）
- 图片间距动态调整，避免重叠

components/canvas/CanvasChatPanel.tsx

@@ -34,6 +34,41 @@ interface CanvasChatPanelProps {
 // 建议卡片数据 - 已移除
 const SUGGESTIONS: { title: string; desc: string; image: string }[] = [];
 
+// 获取图片的原始尺寸
+function getImageDimensions(url: string): Promise<{ width: number; height: number }> {
+  return new Promise((resolve) => {
+    const img = new Image();
+    img.onload = () => {
+      // 限制最大尺寸，避免节点过大
+      const maxSize = 500;
+      let width = img.naturalWidth;
+      let height = img.naturalHeight;
+      
+      // 如果图片太大，按比例缩小
+      if (width > maxSize || height > maxSize) {
+        const scale = Math.min(maxSize / width, maxSize / height);
+        width = Math.round(width * scale);
+        height = Math.round(height * scale);
+      }
+      
+      // 设置最小尺寸
+      const minSize = 150;
+      if (width < minSize && height < minSize) {
+        const scale = minSize / Math.min(width, height);
+        width = Math.round(width * scale);
+        height = Math.round(height * scale);
+      }
+      
+      resolve({ width, height });
+    };
+    img.onerror = () => {
+      // 加载失败时使用默认尺寸
+      resolve({ width: 300, height: 300 });
+    };
+    img.src = url;
+  });
+}
+
 // 从消息中提取图片 URL（只提取原始图片，避免重复）
 function extractImageUrls(text: string): string[] {
   const urls: string[] = [];
@@ -349,7 +384,7 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
     }
     
     // 只处理新消息
-    messages.forEach(message => {
+    messages.forEach(async (message) => {
       if (message.role === 'assistant' && !processedMessageIds.current.has(message.id)) {
         const content = message.parts?.map((p: any) => p.text || '').join('') || '';
         const imageUrls = extractImageUrls(content);
@@ -366,16 +401,22 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
           // 只添加不存在的图片
           const newUrls = imageUrls.filter(url => !existingUrls.has(url));
           
-          newUrls.forEach((url, index) => {
-            // 计算位置（避免重叠）
-            const existingNodes = nodes.length;
-            const x = 100 + ((existingNodes + index) % 4) * 320;
-            const y = 100 + Math.floor((existingNodes + index) / 4) * 320;
+          // 异步获取每张图片的尺寸并添加到画布
+          for (let index = 0; index < newUrls.length; index++) {
+            const url = newUrls[index];
+            // 获取图片原始尺寸
+            const dimensions = await getImageDimensions(url);
+            
+            // 计算位置（避免重叠，根据图片宽度动态调整间距）
+            const existingNodes = nodes.length + index;
+            const spacing = 20; // 图片间距
+            const x = 100 + (existingNodes % 3) * (dimensions.width + spacing);
+            const y = 100 + Math.floor(existingNodes / 3) * (dimensions.height + spacing);
             
             addNode({
               type: 'image',
               position: { x, y },
-              size: { width: 300, height: 300 },
+              size: { width: dimensions.width, height: dimensions.height },
               data: {
                 src: url,
                 status: 'completed',
@@ -383,7 +424,7 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
               },
               connections: [],
             });
-          });
+          }
           
           if (newUrls.length > 0) {
             toast.success(`已将 ${newUrls.length} 张图片添加到画布`);
@@ -605,15 +646,17 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
           }];
         });
         
-        // 立即将图片添加到画布
+        // 获取图片原始尺寸后添加到画布
+        const dimensions = await getImageDimensions(imageUrl);
         const existingNodes = nodes.length;
-        const x = 100 + (existingNodes % 4) * 320;
-        const y = 100 + Math.floor(existingNodes / 4) * 320;
+        const spacing = 20;
+        const x = 100 + (existingNodes % 3) * (dimensions.width + spacing);
+        const y = 100 + Math.floor(existingNodes / 3) * (dimensions.height + spacing);
         
         addNode({
           type: 'image',
           position: { x, y },
-          size: { width: 300, height: 300 },
+          size: { width: dimensions.width, height: dimensions.height },
           data: {
             src: imageUrl,
             status: 'completed',

components/canvas/nodes/ImageNode.tsx

@@ -384,12 +384,12 @@ export function ImageNode({ node, isSelected }: ImageNodeProps) {
         onMouseEnter={() => setIsHovered(true)}
         onMouseLeave={() => setIsHovered(false)}
       >
-        {/* 图片内容 */}
+        {/* 图片内容 - 使用 object-contain 保持原始比例 */}
         {data.src ? (
           <img
             src={data.src}
             alt={data.prompt || "图片"}
-            className="w-full h-full object-cover"
+            className="w-full h-full object-contain bg-muted/30"
             draggable={false}
           />
         ) : data.status === 'generating' ? (