fix:issue #18

Ink Canvas/MainWindow_cs/MW_Screenshot.cs

@@ -1,6 +1,7 @@
-using System;
+using System;
 using System.Drawing.Imaging;
 using System.IO;
+using System.Runtime.InteropServices;
 using System.Windows;
 
 namespace Ink_Canvas {
@@ -35,17 +36,49 @@ namespace Ink_Canvas {
             using (var memoryGraphics = System.Drawing.Graphics.FromImage(bitmap)) {
                 memoryGraphics.CopyFromScreen(rc.X, rc.Y, 0, 0, rc.Size, System.Drawing.CopyPixelOperation.SourceCopy);
                 
-                // 确保目录存在
                 var directory = Path.GetDirectoryName(savePath);
                 if (!Directory.Exists(directory)) {
                     Directory.CreateDirectory(directory);
                 }
-                
-                bitmap.Save(savePath, ImageFormat.Png);
+
+                try {
+                    // 新增双重目录检查
+                    Directory.CreateDirectory(directory); // 防止多线程场景下的竞争条件
+                    bitmap.Save(savePath, ImageFormat.Png);
+                }
+                catch (Exception ex) when (ex is IOException || 
+                                         ex is UnauthorizedAccessException || 
+                                         ex is ExternalException) { // 新增GDI+异常捕获
+                    // 改进备用路径处理
+                    var docPath = Path.Combine(
+                        Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments),
+                        "Auto Saved - Screenshots",
+                        DateTime.Now.ToString("yyyyMMdd"),
+                        Path.GetFileNameWithoutExtension(savePath) + "_retry.png"); // 添加重试后缀
+
+                    try {
+                        var docDir = Path.GetDirectoryName(docPath);
+                        Directory.CreateDirectory(docDir);
+                        bitmap.Save(docPath, ImageFormat.Png);
+                        savePath = docPath;
+                    }
+                    catch (Exception fallbackEx) {
+                        // 最终错误处理
+                        if (!isHideNotification) {
+                            ShowNotification($"截图保存失败: {fallbackEx.Message}");
+                        }
+                        return;
+                    }
+                }
             }
             
             if (!isHideNotification) {
-                ShowNotification($"截图成功保存至 {savePath}");
+                try {
+                    ShowNotification($"截图成功保存至 {savePath}");
+                }
+                catch {
+                    // 防止通知系统自身异常导致崩溃
+                }
             }
         }
 
@@ -57,20 +90,39 @@ namespace Ink_Canvas {
             
             var basePath = Settings.Automation.AutoSavedStrokesLocation;
             var dateFolder = DateTime.Now.ToString("yyyyMMdd");
-            
-            return Path.Combine(
+            var fullPath = Path.Combine(
                 basePath, 
                 "Auto Saved - Screenshots", 
-                dateFolder, 
-                $"{fileName}.png");
+                dateFolder);
+
+            try {
+                if (!Directory.Exists(fullPath)) {
+                    Directory.CreateDirectory(fullPath);
+                }
+            }
+            catch (Exception) {
+                // 如果创建失败则使用文档目录
+                basePath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
+                fullPath = Path.Combine(basePath, "Auto Saved - Screenshots", dateFolder);
+                Directory.CreateDirectory(fullPath);
+            }
+            
+            return Path.Combine(fullPath, $"{fileName}.png");
         }
 
-        // 获取默认文件夹路径
         private string GetDefaultFolderPath() {
             var basePath = Settings.Automation.AutoSavedStrokesLocation;
             var screenshotsFolder = Path.Combine(basePath, "Auto Saved - Screenshots");
-            
-            if (!Directory.Exists(screenshotsFolder)) {
+
+            try {
+                if (!Directory.Exists(screenshotsFolder)) {
+                    Directory.CreateDirectory(screenshotsFolder);
+                }
+            }
+            catch (Exception) {
+                // 如果创建失败则使用文档目录
+                basePath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
+                screenshotsFolder = Path.Combine(basePath, "Auto Saved - Screenshots");
                 Directory.CreateDirectory(screenshotsFolder);
             }