提取Windows中任何文件的缩略图
从任何文件中提取缩略图的最有效方法是什么，而不仅仅是不同大小的图像？
我看了很多，最有希望的是Windows API ShellFile，但这似乎没有正确安装。 我正在使用Windows 7。
前段时间我写了一个ThumbnailProvider，它从Win API加载缩略图。 支持透明图像。 这是实施：
using System; using System.Drawing; using System.Drawing.Imaging; using System.Runtime.InteropServices; using System.IO; namespace ThumbnailGenerator { [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; } public static Bitmap GetThumbnail(string fileName, int width, int height, ThumbnailOptions options) { IntPtr hBitmap = GetHBitmap(Path.GetFullPath(fileName), width, height, options); try { // return a System.Drawing.Bitmap from the hBitmap return GetBitmapFromHBitmap(hBitmap); } finally { // delete HBitmap to avoid memory leaks DeleteObject(hBitmap); } } public static Bitmap GetBitmapFromHBitmap(IntPtr nativeHBitmap) { Bitmap bmp = Bitmap.FromHbitmap(nativeHBitmap); if (Bitmap.GetPixelFormatSize(bmp.PixelFormat) < 32) return bmp; return CreateAlphaBitmap(bmp, PixelFormat.Format32bppArgb); } 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; } } 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); } } } 然后您可以通过以下方式使用它：
int THUMB_SIZE = 256; Bitmap thumbnail = WindowsThumbnailProvider.GetThumbnail( fileName, THUMB_SIZE, THUMB_SIZE, ThumbnailOptions.None);
请记住，使用后需要Dispose（）位图。
这是（令人敬畏的）接受答案的改进版本。 以下内容已更改：
- 使用不安全而不是SetPixel（） – >可以大大提高性能
-
删除整个
isAlphaBitmap检查。 我不知道为什么首先实现它，但我认为没有理由确定两个包含相同内容的图像（我只是返回具有transperancy的Bitmap，无论是否改变了某些内容）[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); [DllImport("msvcrt.dll", CallingConvention = CallingConvention.Cdecl)] public static extern unsafe IntPtr memcpy(void* dst, void* src, UIntPtr count); public static Bitmap GetThumbnail(string fileName, int width, int height, ThumbnailOptions options) { var hBitmap = GetHBitmap(Path.GetFullPath(fileName), width, height, options); try { // return a System.Drawing.Bitmap from the hBitmap return GetBitmapFromHBitmap(hBitmap); } finally { // delete HBitmap to avoid memory leaks DeleteObject(hBitmap); } } public static Bitmap GetBitmapFromHBitmap(IntPtr nativeHBitmap) { Bitmap bmp = Image.FromHbitmap(nativeHBitmap); if (Image.GetPixelFormatSize(bmp.PixelFormat) < 32) return bmp; using (bmp) return CreateAlphaBitmap(bmp, PixelFormat.Format32bppArgb); } public static unsafe Bitmap CreateAlphaBitmap(Bitmap srcBitmap, PixelFormat targetPixelFormat) { var result = new Bitmap(srcBitmap.Width, srcBitmap.Height, targetPixelFormat); var bmpBounds = new Rectangle(0, 0, srcBitmap.Width, srcBitmap.Height); var srcData = srcBitmap.LockBits(bmpBounds, ImageLockMode.ReadOnly, srcBitmap.PixelFormat); var destData = result.LockBits(bmpBounds, ImageLockMode.ReadOnly, targetPixelFormat); var srcDataPtr = (byte*) srcData.Scan0; var destDataPtr = (byte*) destData.Scan0; try { for (int y = 0; y <= srcData.Height - 1; y++) { for (int x = 0; x <= srcData.Width - 1; x++) { //this is really important because one stride may be positive and the other negative var position = srcData.Stride * y + 4 * x; var position2 = destData.Stride * y + 4 * x; memcpy(destDataPtr + position2, srcDataPtr + position, (UIntPtr) 4); } } } finally { srcBitmap.UnlockBits(srcData); result.UnlockBits(destData); } return result; } 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); } [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) } [ComImport] [Guid("bcc18b79-ba16-442f-80c4-8a59c30c463b")] [InterfaceType(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; } }