Ok, home again. First thing, You'll need this class:
public class IImaging
{
#region stałe i struktury
public enum PixelFormatID : int
{
PixelFormatIndexed = 0x00010000,
PixelFormatGDI = 0x00020000,
PixelFormatAlpha = 0x00040000,
PixelFormatPAlpha = 0x00080000,
PixelFormatExtended = 0x00100000,
PixelFormatCanonical = 0x00200000,
PixelFormatUndefined = 0,
PixelFormatDontCare = 0,
PixelFormat1bppIndexed = (1 | (1 << 8) | PixelFormatIndexed | PixelFormatGDI),
PixelFormat4bppIndexed = (2 | (4 << 8) | PixelFormatIndexed | PixelFormatGDI),
PixelFormat8bppIndexed = (3 | (8 << 8) | PixelFormatIndexed | PixelFormatGDI),
PixelFormat16bppRGB555 = (5 | (16 << 8) | PixelFormatGDI),
PixelFormat16bppRGB565 = (6 | (16 << 8) | PixelFormatGDI),
PixelFormat16bppARGB1555 = (7 | (16 << 8) | PixelFormatAlpha | PixelFormatGDI),
PixelFormat24bppRGB = (8 | (24 << 8) | PixelFormatGDI),
PixelFormat32bppRGB = (9 | (32 << 8) | PixelFormatGDI),
PixelFormat32bppARGB = (10 | (32 << 8) | PixelFormatAlpha | PixelFormatGDI | PixelFormatCanonical),
PixelFormat32bppPARGB = (11 | (32 << 8) | PixelFormatAlpha | PixelFormatPAlpha | PixelFormatGDI),
PixelFormat48bppRGB = (12 | (48 << 8) | PixelFormatExtended),
PixelFormat64bppARGB = (13 | (64 << 8) | PixelFormatAlpha | PixelFormatCanonical | PixelFormatExtended),
PixelFormat64bppPARGB = (14 | (64 << 8) | PixelFormatAlpha | PixelFormatPAlpha | PixelFormatExtended),
PixelFormatMax = 15
}
public enum BufferDisposalFlag : int
{
BufferDisposalFlagNone,
BufferDisposalFlagGlobalFree,
BufferDisposalFlagCoTaskMemFree,
BufferDisposalFlagUnmapView
}
public enum InterpolationHint : int
{
InterpolationHintDefault,
InterpolationHintNearestNeighbor,
InterpolationHintBilinear,
InterpolationHintAveraging,
InterpolationHintBicubic
}
public struct BitmapData
{
public uint Width;
public uint Height;
public int Stride;
public PixelFormatID PixelFormat;
public IntPtr Scan0;
public IntPtr Reserved;
}
public struct ImageInfo
{
public uint GuidPart1;
public uint GuidPart2;
public uint GuidPart3;
public uint GuidPart4;
public PixelFormatID pixelFormat;
public uint Width;
public uint Height;
public uint TileWidth;
public uint TileHeight;
public double Xdpi;
public double Ydpi;
public uint Flags;
}
#endregion
#region interfejsy
[ComImport, Guid("327ABDA7-072B-11D3-9D7B-0000F81EF32E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[ComVisible(true)]
public interface IImagingFactory
{
uint CreateImageFromStream(IStream stream, out IImage image);
uint CreateImageFromFile(string filename, out IImage image);
uint CreateImageFromBuffer([MarshalAs(UnmanagedType.LPArray)] byte[] buffer, uint size, BufferDisposalFlag disposalFlag, out IImage image);
uint CreateNewBitmap(uint width, uint height, PixelFormatID pixelFormat, out IBitmapImage bitmap);
uint CreateBitmapFromImage(IImage image, uint width, uint height, PixelFormatID pixelFormat, InterpolationHint hints, out IBitmapImage bitmap);
uint CreateBitmapFromBuffer(BitmapData bitmapData, out IBitmapImage bitmap);
uint CreateImageDecoder(); // pominięte
uint CreateImageEncoderToStream(); // pominięte
uint CreateImageEncoderToFile(); // pominięte
uint GetInstalledDecoders(); // pominięte
uint GetInstalledEncoders(); // pominięte
uint InstallImageCodec(); // pominięte
uint UninstallImageCodec(); // pominięte
}
[ComImport, Guid("327ABDA9-072B-11D3-9D7B-0000F81EF32E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[ComVisible(true)]
public interface IImage
{
uint GetPhysicalDimension(out Size size);
uint GetImageInfo(out ImageInfo info);
uint SetImageFlags(uint flags);
uint Draw(IntPtr hdc, ref Rectangle dstRect, IntPtr srcRect);
uint PushIntoSink(); // pominięte
uint GetThumbnail(uint thumbWidth, uint thumbHeight, out IImage thumbImage);
}
[ComImport, Guid("327ABDAA-072B-11D3-9D7B-0000F81EF32E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[ComVisible(true)]
public interface IBitmapImage
{
uint GetSize(out Size size);
uint GetPixelFormatID(out PixelFormatID pixelFormat);
uint LockBits(ref Rectangle rect, uint flags, PixelFormatID pixelFormat, out BitmapData lockedBitmapData);
uint UnlockBits(ref BitmapData lockedBitmapData);
uint GetPalette(); // pominięte
uint SetPalette(); // pominięte
}
[ComImport, Guid("0000000c-0000-0000-C000-000000000046"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[ComVisible(true)]
public interface IStream
{
void Read([Out, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] byte[] pv, int cb, IntPtr pcbRead);
void Write([MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] byte[] pv, int cb, IntPtr pcbWritten);
void Seek(long dlibMove, int dwOrigin, IntPtr plibNewPosition);
void SetSize(long libNewSize);
void CopyTo(IStream pstm, long cb, IntPtr pcbRead, IntPtr pcbWritten);
void Commit(int grfCommitFlags);
void Revert();
void LockRegion(long libOffset, long cb, int dwLockType);
void UnlockRegion(long libOffset, long cb, int dwLockType);
void Stat(); // pominięte
void Clone(out IStream ppstm);
}
#endregion
#region metody
public static IImagingFactory CreateFactory()
{
return (IImagingFactory)Activator.CreateInstance(Type.GetTypeFromCLSID(new Guid("327ABDA8-072B-11D3-9D7B-0000F81EF32E")));
}
#endregion
}
It's 80% implementation of IImaging API. I've skipped some methods (the ones with "// pominięte" :)) because those require more playing with structures and interfaces than it's worth.
Now all You need to do is to:
IImagingFactory factory = IImaging.CreateFactory();
IImage image;
IImage thumbnail;
factory.CreateImageFromFile(path, out image);
image.GetThumbnail(100, 100, out thumbnail);
Image img = new Bitmap(100, 100);
Rectangle rect = new Rectangle(img.Width, img.Height);
using(Graphics g = Graphics.FromImage(img))
{
IntPtr hdc = g.GetHdc();
thumbnail.Draw(hdc, ref rect, IntPtr.Zero);
g.ReleaseHdc(hdc);
}
thumbnail.Release();
image.Release();
factory.Release();
First thing, I'm initializing the factory and getting an image from the path. After that I'm creating a thumbnail and creating a bitmap (managed) which will serve as a managed 'canvas' for our thumbnail. Next I'm getting HDC of that 'canvas' and paint upon it our thumbnail from IImage.
Now You can do whatever You wish with a managed bitmap 'containing' Your thumbnail (save, draw etc.).
Hope it's clean enough to understand.
If You'll find my answer satisfactory or helpful - mark it as answered or vote for it! Thank You.
If You think You know better then me, why is Your code not working, then don't waste my time at this forum. Otherwise - do as I'm suggesting.
I'm on MSDN just like MD House in the clinic. But I'm also a human which sometimes needs to see another doctor :)
