增强预览机制

bin/util/vips.dart

@@ -7,25 +7,82 @@ class Vips {
 
   Vips({this.vipsExecuteFile});
 
-  Future<File> generatePreview(String imgPath) async {
-    final imgOut =
-        "cache/preview/" + basename(imgPath).hashCode.toString() + ".webp";
+  /// 生成图片预览（WebP 格式）
+  /// 
+  /// [imgPath] 原图路径
+  /// [w] 预览图宽度（可选）
+  /// [h] 预览图高度（可选）
+  /// 
+  /// 如果同时指定 [w] 和 [h]，图片将按比例缩放以适应指定尺寸
+  Future<File> generatePreview(
+    String imgPath, {
+    int? w,
+    int? h,
+  }) async {
+    // 生成缓存文件名：包含原图 hash 和尺寸信息
+    final baseName = basename(imgPath).hashCode.toString();
+    final sizeSuffix = _buildSizeSuffix(w, h);
+    final imgOut = "cache/preview/${baseName}${sizeSuffix}.webp";
     final outFile = File(imgOut);
+    
+    // 缓存命中：直接返回已存在的预览图
     if (outFile.existsSync()) {
       return outFile;
     }
-    final result = await Process.run("vips", [
-      "webpsave",
-      imgPath,
-      imgOut,
-      "--Q",
-      "80",
-      "--smart-subsample",
-      "--strip",
-    ]);
-    if (result.exitCode == 0) {
+
+    // 确保缓存目录存在
+    await outFile.parent.create(recursive: true);
+
+    // 构建 vips 命令参数
+    if (w != null || h != null) {
+      final thumbnailArgs = <String>[
+        "thumbnail",
+        imgPath,
+        imgOut,
+        w?.toString() ?? "0",
+        "--height",
+        h?.toString() ?? "0",
+      ];
+
+      final thumbnailResult = await Process.run("vips", thumbnailArgs);
+      if (thumbnailResult.exitCode != 0) {
+        print(thumbnailResult.stderr);
+        throw Exception("vips thumbnail failed!");
+      }
       return outFile;
+    } else {
+      // 不缩放，直接转换为 WebP 格式
+      final args = <String>[
+        "webpsave",
+        imgPath,
+        imgOut,
+        "--Q",
+        "80",
+        "--effort",
+        "6",
+        "--smart-subsample",
+      ];
+
+      final result = await Process.run("vips", args);
+      if (result.exitCode == 0) {
+        return outFile;
+      }
+      print(result.stderr);
+      throw Exception("vips image transcode failed!");
     }
-    throw Exception("vips image transcode failed!");
+  }
+
+  /// 构建尺寸后缀
+  /// 
+  /// 例如：
+  /// - w=200, h=150 => "_200x150"
+  /// - w=200, h=null => "_200x0"
+  /// - w=null, h=150 => "_0x150"
+  /// - w=null, h=null => ""
+  String _buildSizeSuffix(int? w, int? h) {
+    if (w == null && h == null) {
+      return "";
+    }
+    return "_${w ?? 0}x${h ?? 0}";
   }
 }