Каков наиболее эффективный способ извлечения миниатюр из любого файла, а не просто изображений с разными размерами?
Я просмотрел все, наиболее перспективным из которых был Windows API ShellFile, но это, похоже, не было правильно установлено. Я использую окна 7.
Некоторое время назад я написал ThumbnailProvider, который загружает миниатюру из Win API. Поддержка прозрачных изображений. Это реализация:
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);
}
}
}
Затем вы можете использовать его следующим образом:
int THUMB_SIZE = 256;
Bitmap thumbnail = WindowsThumbnailProvider.GetThumbnail(
fileName, THUMB_SIZE, THUMB_SIZE, ThumbnailOptions.None);
Помните, что после использования Dispose() растровое изображение.
Это улучшенная версия (удивительного) ответа, который был принят. Изменено следующее:
удалить всю проверку isAlphaBitmap. Я понятия не имею, почему это было реализовано в первую очередь, но я не вижу смысла определять между двумя изображениями, которые содержат одинаковый контент (я просто возвращаю растровое изображение с прозрачностью, независимо от того, изменилось ли это что-то)
[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;
}
}