背景：因前有OfficeOnline的搭建，所以搭建完之后领导又提出要求啦，说：小xu，你……你把这文件的缩略图给我整出来吧。经过我历时久远的研究（这个问题跨了个年，随着2020疫情的发展，还过了两个月，放了个大长假）。但终，解决了，心头大患也。
嗯~巴适~
好啦，正戏正儿八经开始了！现在这里有两种解决方案，且听我细细说来~
使用普通方法截取文件图片
优点：① 所有文件都可以被截取；
缺点：① 除PPT外截取的都是文件的图标；
② 截取图片比较模糊；
③ 截取图片有黑边；
如下图：
代码
[Flags] public enum ThumbnailOptions { None = 0x00, BiggerSizeOk = 0x01, InMemoryOnly = 0x02, IconOnly = 0x04, ThumbnailOnly = 0x08, InCacheOnly = 0x10, } public class WindowsThumbnailProvider { private const string IShellItem2Guid = "7E9FB0D3-919F-4307-AB2E-9B1860310C93"; [DllImport("shell32.dll", CharSet = CharSet.Unicode, SetLastError = true)] internal static extern int SHCreateItemFromParsingName( [MarshalAs(UnmanagedType.LPWStr)] string path, // The following parameter is not used - binding context. IntPtr pbc, ref Guid riid, [MarshalAs(UnmanagedType.Interface)] out IShellItem shellItem); [DllImport("gdi32.dll")] [return: MarshalAs(UnmanagedType.Bool)] internal static extern bool DeleteObject(IntPtr hObject); [ComImport] [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] [Guid("43826d1e-e718-42ee-bc55-a1e261c37bfe")] internal interface IShellItem { void BindToHandler(IntPtr pbc, [MarshalAs(UnmanagedType.LPStruct)]Guid bhid, [MarshalAs(UnmanagedType.LPStruct)]Guid riid, out IntPtr ppv); void GetParent(out IShellItem ppsi); void GetDisplayName(SIGDN sigdnName, out IntPtr ppszName); void GetAttributes(uint sfgaoMask, out uint psfgaoAttribs); void Compare(IShellItem psi, uint hint, out int piOrder); }; internal enum SIGDN : uint { NORMALDISPLAY = 0, PARENTRELATIVEPARSING = 0x80018001, PARENTRELATIVEFORADDRESSBAR = 0x8001c001, DESKTOPABSOLUTEPARSING = 0x80028000, PARENTRELATIVEEDITING = 0x80031001, DESKTOPABSOLUTEEDITING = 0x8004c000, FILESYSPATH = 0x80058000, URL = 0x80068000 } internal enum HResult { Ok = 0x0000, False = 0x0001, InvalidArguments = unchecked((int)0x80070057), OutOfMemory = unchecked((int)0x8007000E), NoInterface = unchecked((int)0x80004002), Fail = unchecked((int)0x80004005), ElementNotFound = unchecked((int)0x80070490), TypeElementNotFound = unchecked((int)0x8002802B), NoObject = unchecked((int)0x800401E5), Win32ErrorCanceled = 1223, Canceled = unchecked((int)0x800704C7), ResourceInUse = unchecked((int)0x800700AA), AccessDenied = unchecked((int)0x80030005) } [ComImportAttribute()] [GuidAttribute("bcc18b79-ba16-442f-80c4-8a59c30c463b")] [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)] internal interface IShellItemImageFactory { [PreserveSig] HResult GetImage( [In, MarshalAs(UnmanagedType.Struct)] NativeSize size, [In] ThumbnailOptions flags, [Out] out IntPtr phbm); } [StructLayout(LayoutKind.Sequential)] internal struct NativeSize { private int width; private int height; public int Width { set { width = value; } } public int Height { set { height = value; } } }; [StructLayout(LayoutKind.Sequential)] public struct RGBQUAD { public byte rgbBlue; public byte rgbGreen; public byte rgbRed; public byte rgbReserved; } ////// 获取缩略图 /// /// 文件所在绝对路径 /// 图片宽 /// 图片高 /// public static void GetThumbnail(string filePath, string imgFullPath, int width, int height, ThumbnailOptions options) { IntPtr hBitmap = GetHBitmap(Path.GetFullPath(filePath), width, height, options); try { SaveBitmap(hBitmap, imgFullPath); } catch { throw; } finally { DeleteObject(hBitmap); } } /// /// 将Bitmap转换成图片，并返回缩略图相对路径 /// /// /// 文件名称 /// public static void SaveBitmap(IntPtr hBitmap, string imgFullPath) { try { Bitmap bmp = GetBitmapFromHBitmap(hBitmap); bmp.Save(imgFullPath, ImageFormat.Jpeg); } catch (IOException ex) { throw ex; } } /// /// 将HBitmap转换成Bitmap /// /// /// public static Bitmap GetBitmapFromHBitmap(IntPtr nativeHBitmap) { Bitmap bmp = Bitmap.FromHbitmap(nativeHBitmap); if (Bitmap.GetPixelFormatSize(bmp.PixelFormat) < 32) return bmp; return CreateAlphaBitmap(bmp, PixelFormat.Format32bppArgb); } /// /// 创建图片 /// /// /// /// public static Bitmap CreateAlphaBitmap(Bitmap srcBitmap, PixelFormat targetPixelFormat) { Bitmap result = new Bitmap(srcBitmap.Width, srcBitmap.Height, targetPixelFormat); Rectangle bmpBounds = new Rectangle(0, 0, srcBitmap.Width, srcBitmap.Height); BitmapData srcData = srcBitmap.LockBits(bmpBounds, ImageLockMode.ReadOnly, srcBitmap.PixelFormat); bool isAlplaBitmap = false; try { for (int y = 0; y <= srcData.Height - 1; y++) { for (int x = 0; x <= srcData.Width - 1; x++) { Color pixelColor = Color.FromArgb( Marshal.ReadInt32(srcData.Scan0, (srcData.Stride * y) + (4 * x))); if (pixelColor.A > 0 & pixelColor.A < 255) { isAlplaBitmap = true; } result.SetPixel(x, y, pixelColor); } } } finally { srcBitmap.UnlockBits(srcData); } if (isAlplaBitmap) { return result; } else { return srcBitmap; } } /// /// GetHBitmap /// /// /// /// /// /// private static IntPtr GetHBitmap(string fileName, int width, int height, ThumbnailOptions options) { IShellItem nativeShellItem; Guid shellItem2Guid = new Guid(IShellItem2Guid); int retCode = SHCreateItemFromParsingName(fileName, IntPtr.Zero, ref shellItem2Guid, out nativeShellItem); if (retCode != 0) throw Marshal.GetExceptionForHR(retCode); NativeSize nativeSize = new NativeSize(); nativeSize.Width = width; nativeSize.Height = height; IntPtr hBitmap; HResult hr = ((IShellItemImageFactory)nativeShellItem).GetImage(nativeSize, options, out hBitmap); Marshal.ReleaseComObject(nativeShellItem); if (hr == HResult.Ok) return hBitmap; throw Marshal.GetExceptionForHR((int)hr); } }
如何使用
//string filePath = "E:\\File\\我就是很开心.txt";//文件所在位置 //string filePath = "E:\\File\\我有点不开心.xlsx";//文件所在位置 //string filePath = "E:\\File\\你看起来很好吃.docx";//文件所在位置 string filePath = "E:\\File\\项目测试使用文件.pptx";//文件所在位置 //自定义图片路径 string imgName = Path.GetFileName(filePath).Split('.')[0]; string direcName = Path.GetDirectoryName(filePath); string imgFullPath = $"{direcName}\\{imgName}.jpg";//重组，获取图片存放位置 int pic_size = 1000; WindowsThumbnailProvider.GetThumbnail(filePath, imgFullPath, pic_size, pic_size, ThumbnailOptions.None);
使用Aspose截取文件图片
注意：Aspose自身可以截取所有文件，但我这里设置的目前只能截取rar、ppt、excel、word这四种格式，其他格式就会报错。你如果需要更多的文件格式截图，就再进行研究就阔以。该dll中的方法可以截取多张图片，不一定就是文件首页。笔芯~
去水印
如果没有破解码，直接使用aspose，打印出来的照片就会有水印。如下图：
所以你需要在App.config中，添加一个节点，如下：
（注：web项目对应的是web.config;控制台项目对应的是app.config,不过下面节点在两种文件里面都通用)
<add key="AsposeKey" value="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" />
注：使用此码是对aspose各个dll的版本有要求的，需要在2015年12月30日之前的版本，才可以使用。所以你可以去nuget官网（https://www.nuget.org/packages?q=Aspose.Words）查找相应日期对应的版本。如果你懒，你懒，懒……，不用担心，我给你找好了。
| 名称 |
版本 |
日期 |
| Aspose.Words |
15.12.0 |
2015/12/26 |
| Aspose.Excel |
8.6.3 |
2015/12/23 |
| Aspose.Slides |
15.10.0.0 |
2015/12/10 |
| Aspose.Pdf |
11.1.1.0 |
2015/12/30 |
代码
详见下面的链接中的解决方案吧，不想复制了，实在是太多啦。
如何使用
//string filePath = "E:\\File\\我就是很开心.txt";//文件所在位置 //string filePath = "E:\\File\\我有点不开心.xlsx";//文件所在位置 //string filePath = "E:\\File\\你看起来很好吃.docx";//文件所在位置 string filePath = "E:\\File\\项目测试使用文件.pptx";//文件所在位置 //自定义图片路径 string imgName = Path.GetFileName(filePath).Split('.')[0]; string direcName = Path.GetDirectoryName(filePath); string imgFullPath = $"{direcName}\\{imgName}.jpg";//重组，获取图片存放位置 string extendName = Path.GetExtension(filePath); //这里运用的是简单工厂模式 ImageConverterFactory factory = new ImageConverterFactory(); var imageConvert = factory.CreateImageConverter(extendName); imageConvert.ConvertToImage(filePath, imgFullPath);
代码下载
两种方法在同一个解决方案里
百度云盘：链接：https://pan.baidu.com/s/10edFyh1W_6zYjcTVmXFGEQ 提取码：1l4t
感谢大佬的热心分享：https://www.cnblogs.com/zhuweisky/p/4774803.html
有什么不明白的可随时评论，我看到就会回复哦~
看到这了，小主大人，手留余香，点个赞白~