timage rotation

how can a timage be rotated in a fix angle say 90 degress
can any body help me..
this is an easy point.
may the force be with you.....
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Maybe this : from UDDF :}
From: Dave Shapiro <daves@cyber-fx.com>

Counterclockwise, that is. This rotates a 640x480 24-bit bitmap 90 degrees
in about 2/10 of sec on my P133 (4MB video card, 128MB RAM). It works
for Delphi 2, and should work for 1 and 3, too.

One thing: This does not work for bitmaps that aren't an integral number of
colors per pixel. If that's the case, you'll have to do some bit twiddling. I'm
working on that part right now (I need it too), but it'll be a few days. Anyways,
suggestions, comments, etc., always welcome.

Special thanks to David Ullrich (ooh, I hope I spelled that correctly) for
pointing out the non-published-but-public-anyway SaveToStream method for
the TBitmap class.

Advance apologies for any formatting problems. Netscape's editor is so
ridiculously crippled that I can't accomplish anything (give me rtin and vim
any day).

procedure RotateBitmap90Degrees(ABitmap: TBitmap);

  BITMAP_HEADER_SIZE = SizeOf(TBitmapFileHeader) +

  { Things that end in R are for the rotated image. }
  PbmpInfoR: PBitmapInfoHeader;
  bmpBuffer, bmpBufferR: PByte;
  MemoryStream, MemoryStreamR: TMemoryStream;
  PbmpBuffer, PbmpBufferR: PByte;
  PbmpBufferRFirstScanLine, PbmpBufferColumnZero: PByte;
  BytesPerPixel, BytesPerScanLine, BytesPerScanLineR: Integer;
  X, Y, T: Integer;

    Don't *ever* call GetDIBSizes! It screws up your bitmap.
    I'll be posting about that shortly.

  MemoryStream := TMemoryStream.Create;

   To do: Put in a SetSize, which will eliminate any reallocation


   Don't need you anymore. We'll make a new one when the time comes.

  bmpBuffer := MemoryStream.Memory;

  { Set PbmpInfoR to point to the source bitmap's info header. }
  { Boy, these headers are getting annoying. }
  Inc( bmpBuffer, SizeOf(TBitmapFileHeader) );
  PbmpInfoR := PBitmapInfoHeader(bmpBuffer);

  { Set bmpBuffer to point to the original bitmap bits. }
  Inc(bmpBuffer, SizeOf(PbmpInfoR^));
  { Set the ColumnZero pointer to point to, uh, column zero. }
  PbmpBufferColumnZero := bmpBuffer;

  with PbmpInfoR^ do
    BytesPerPixel := biBitCount shr 3;
    { ScanLines are DWORD aligned. }
    BytesPerScanLine := ((((biWidth * biBitCount) + 31) div 32) * SizeOf(DWORD));
    BytesPerScanLineR := ((((biHeight * biBitCount) + 31) div 32) * SizeOf(DWORD));

    { The TMemoryStream that will hold the rotated bits. }
    MemoryStreamR := TMemoryStream.Create;
     Set size for rotated bitmap. Might be different from source size
     due to DWORD aligning.
    MemoryStreamR.SetSize(BITMAP_HEADER_SIZE  + BytesPerScanLineR * biWidth);

  { Copy the headers from the source bitmap. }
  MemoryStream.Seek(0, soFromBeginning);
  MemoryStreamR.CopyFrom(MemoryStream, BITMAP_HEADER_SIZE);

  { Here's the buffer we're going to rotate. }
  bmpBufferR := MemoryStreamR.Memory;
  { Skip the headers, yadda yadda yadda... }
  Inc(bmpBufferR, BITMAP_HEADER_SIZE);

   Set up PbmpBufferRFirstScanLine and advance it to end of the first scan
   line of bmpBufferR.
  PbmpBufferRFirstScanLine := bmpBufferR;
  Inc(PbmpBufferRFirstScanLine, (PbmpInfoR^.biHeight - 1) * BytesPerPixel);

  { Here's the meat. Loop through the pixels and rotate appropriately. }

  { Remember that DIBs have their origins opposite from DDBs. }
  for Y := 1 to PbmpInfoR^.biHeight do
    PbmpBuffer := PbmpBufferColumnZero;
    PbmpBufferR := PbmpBufferRFirstScanLine;

    for X := 1 to PbmpInfoR^.biWidth do
      for T := 1 to BytesPerPixel do
        PbmpBufferR^ := PbmpBuffer^;
      Dec(PbmpBufferR, BytesPerPixel);
      Inc(PbmpBufferR, BytesPerScanLineR);

    Inc(PbmpBufferColumnZero, BytesPerScanLine);
    Dec(PbmpBufferRFirstScanLine, BytesPerPixel);

  { Done with the source bits. }

  { Now set PbmpInfoR to point to the rotated bitmap's info header. }
  PbmpBufferR := MemoryStreamR.Memory;
  Inc( PbmpBufferR, SizeOf(TBitmapFileHeader) );
  PbmpInfoR := PBitmapInfoHeader(PbmpBufferR);

  { Swap the width and height of the rotated bitmap's info header. }
  with PbmpInfoR^ do
    T := biHeight;
    biHeight := biWidth;
    biWidth := T;

  ABitmap := TBitmap.Create;

  { Spin back to the very beginning. }
  MemoryStreamR.Seek(0, soFromBeginning);


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