{
 This function performs a 2D convolution on an image.
 It can be used for a very wide range of image processing operations
 such as image smoothing, anti-aliasing, edge detection,
 detail enhancment, etc. It is very fast.
}
 uses
  Graphics, Windows;
 type
  TRGBTripleArray = array[0..10000] of TRGBTriple;
  PRGBTripleArray = ^TRGBTripleArray;
  T3x3FloatArray = array[0..2] of array[0..2] of Extended;
 implementation
 function Convolve(ABitmap: TBitmap; AMask: T3x3FloatArray;
  ABias: Integer): TBitmap;
 var
  LRow1, LRow2, LRow3, LRowOut: PRGBTripleArray;
  LRow, LCol: integer;
  LNewBlue, LNewGreen, LNewRed: Extended;
  LCoef: Extended;
 begin
  LCoef := 0;
  for LRow := 0 to 2 do
  for LCol := 0 to 2 do
  LCoef := LCoef + AMask[LCol, LRow];
  if LCoef = 0 then LCoef := 1;
  Result := TBitmap.Create;
  Result.Width := ABitmap.Width - 2;
  Result.Height := ABitmap.Height - 2;
  Result.PixelFormat := pf24bit;
  LRow2 := ABitmap.ScanLine[0];
  LRow3 := ABitmap.ScanLine[1];
  for LRow := 1 to ABitmap.Height - 2 do
  begin
  LRow1 := LRow2;
  LRow2 := LRow3;
  LRow3 := ABitmap.ScanLine[LRow + 1];
  LRowOut := Result.ScanLine[LRow - 1];
  for LCol := 1 to ABitmap.Width - 2 do
  begin
  LNewBlue :=
  (LRow1[LCol - 1].rgbtBlue * AMask[0,0]) + (LRow1[LCol].rgbtBlue * AMask[1,0]) +
  (LRow1[LCol + 1].rgbtBlue * AMask[2,0]) +
  (LRow2[LCol - 1].rgbtBlue * AMask[0,1]) + (LRow2[LCol].rgbtBlue * AMask[1,1]) +
  (LRow2[LCol + 1].rgbtBlue * AMask[2,1]) +
  (LRow3[LCol - 1].rgbtBlue * AMask[0,2]) + (LRow3[LCol].rgbtBlue * AMask[1,2]) +
  (LRow3[LCol + 1].rgbtBlue * AMask[2,2]);
  LNewBlue := (LNewBlue / LCoef) + ABias;
  if LNewBlue > 255 then
  LNewBlue := 255;
  if LNewBlue < 0 then
  LNewBlue := 0;
  LNewGreen :=
  (LRow1[LCol - 1].rgbtGreen * AMask[0,0]) + (LRow1[LCol].rgbtGreen * AMask[1,0]) +
  (LRow1[LCol + 1].rgbtGreen * AMask[2,0]) +
  (LRow2[LCol - 1].rgbtGreen * AMask[0,1]) + (LRow2[LCol].rgbtGreen * AMask[1,1]) +
  (LRow2[LCol + 1].rgbtGreen * AMask[2,1]) +
  (LRow3[LCol - 1].rgbtGreen * AMask[0,2]) + (LRow3[LCol].rgbtGreen * AMask[1,2]) +
  (LRow3[LCol + 1].rgbtGreen * AMask[2,2]);
  LNewGreen := (LNewGreen / LCoef) + ABias;
  if LNewGreen > 255 then
  LNewGreen := 255;
  if LNewGreen < 0 then
  LNewGreen := 0;
  LNewRed :=
  (LRow1[LCol - 1].rgbtRed * AMask[0,0]) + (LRow1[LCol].rgbtRed * AMask[1,0])
  + (LRow1[LCol + 1].rgbtRed * AMask[2,0]) +
  (LRow2[LCol - 1].rgbtRed * AMask[0,1]) + (LRow2[LCol].rgbtRed * AMask[1,1])
  + (LRow2[LCol + 1].rgbtRed * AMask[2,1]) +
  (LRow3[LCol - 1].rgbtRed * AMask[0,2]) + (LRow3[LCol].rgbtRed * AMask[1,2])
  + (LRow3[LCol + 1].rgbtRed * AMask[2,2]);
  LNewRed := (LNewRed / LCoef) + ABias;
  if LNewRed > 255 then
  LNewRed := 255;
  if LNewRed < 0 then
  LNewRed := 0;
  LRowOut[LCol - 1].rgbtBlue := trunc(LNewBlue);
  LRowOut[LCol - 1].rgbtGreen := trunc(LNewGreen);
  LRowOut[LCol - 1].rgbtRed := trunc(LNewRed);
  end;
  end;
 end;
 // example use
// edge detection
procedure TForm1.Button1Click(Sender: TObject);
 var
  LMask: T3x3FloatArray;
 begin
  LMask[0,0] := -1;
  LMask[1,0] := -1;
  LMask[2,0] := -1;
  LMask[0,1] := -1;
  LMask[1,1] := 8;
  LMask[2,1] := -1;
  LMask[0,2] := -1;
  LMask[1,2] := -1;
  LMask[2,2] := -1;
  Image1.Picture.Bitmap := Convolve(Image1.Picture.Bitmap, LMask, 0);
 end;