IThumbnailCache - Thumbnail ermitteln

[KarstenK]

image3.Picture.Bitmap.Handle := hbmp;

Ich bin nicht sicher ob das reicht, ich verwende für DIB per handle eine extra funktion die aus dem Handle ein richtiges TBitmap macht.

Delphi-Quellcode:

//*****************************************************************************************
// efg, June 2000.  efg's Computer Lab, www.efg2.com/Lab
//
// Contents
//
//      Method 2.  hDIB to TBitmap resulting in bmDIB using MemoryStream (best)
//
// Summary:
//
//      Method 1.  hDIB to TBitmap resulting in bmDDB using StretchDIBits
//      Method 2.  hDIB to TBitmap resulting in bmDIB using MemoryStream
//      Method 3.  pf24bit TBitmap created using L_PaintDC Lead API call
//
// Tests:
//
//      A.  Deer.BMP, 160 by 194, 8 bits/pixel, palette mostly of browns
//
//                   256 color display     true color display (24-bit)
//                   400 MHz Pentium       166 MHz Pentium
//                   ------------------    -----------------
//      Method 1     15 ms always works    12 ms white bar (~10%) 1 of 4 times
//      Method 2      7 ms always works     4 ms always works
//      Method 3      6 ms bad color       21 ms bad color
//
//
//      B.  Balloons.BMP, 768 by 512, 24 bits/pixel, no palette
//
//                   256 color display     true color display (24-bit)
//                   400 MHz Pentium       166 MHz Pentium
//                   ------------------    -----------------
//      Method 1      82 ms bad color      189 ms always works.
//      Method 2      74 ms OK color       261 ms always works
//      Method 3     155 ms bad color      289 ms always works
//
// ============================================================================
// Method 2.  hDIB to TBitmap resulting in bmDIB using MemoryStream.
// Anatomy of a DIB written to stream :
// 1.  Bitmap File Header.  Normally 14 bytes, i.e., SizeOf(TBitmapFileHeader).
// 2.  Bitmap Info Header.  Normally 40 bytes, i.e., SizeOf(TBitmapInfoHeader)
// 3.  Color Table.  Bitmaps with > 256 colors do not have a color table.
// 4.  Bitmap Bits.
//
// Based on 12 July 1998 UseNet post "DIB to TBitmap" by Taine Gilliam in
// borland.public.delphi.vcl.components.using

function hDIBToTBitmap(const hDIB: THandle): TBitmap;

var
  BitCount: INTEGER;
  BitmapFileHeader: TBitmapFileHeader;
  BitmapInfo: pBitmapInfo;
  DIBinMemory: Pointer;
  MemoryStream: TMemoryStream;
  NumberOfColors: INTEGER;
begin
  RESULT := TBitmap.Create;

  DIBinMemory := GlobalLock(hDIB);
  try
    BitmapInfo := DIBInMemory;
    NumberOfColors := BitmapInfo.bmiHeader.biClrUsed;
    BitCount := BitmapInfo.bmiHeader.biBitCount;
    if (NumberOfColors = 0) and (BitCount <= 8) then
      NumberOfColors := 1 shl BitCount;

    with BitmapFileHeader do
      begin
        bfType := $4D42; // 'BM'
        bfReserved1 := 0;
        bfReserved2 := 0;
        bfOffBits := SizeOf(TBitmapFileHeader) +
          SizeOf(TBitmapInfoHeader) +
          NumberOfColors * SizeOf(TRGBQuad);
        bfSize := bfOffBits + BitmapInfo.bmiHeader.biSizeImage;
      end;

    MemoryStream := TMemoryStream.Create;
    try
      MemoryStream.Write(BitmapFileHeader, SizeOf(TBitmapFileHeader));
      MemoryStream.Write(DIBInMemory^,
        BitmapFileHeader.bfSize - SizeOf(TBitmapFileHeader));
      MemoryStream.Position := 0;
      RESULT.LoadFromStream(MemoryStream)
    finally
      MemoryStream.Free
    end

  finally
    GlobalUnlock(hDIB);
    GlobalFree(hDIB)
  end
end {hDIBToTBitmap};