function ColorFill(Bitmap: TBitmap; FillColor: TColor): Boolean;
(************************************************************************
  This function is PUBLIC DOMAIN.

  The function takes a VCL TBitmap object and the FillColor (as TColor
  value) as parameters. There is the limitation, that the following
  color values are simply senseless and therefore unsupported: clNone and
  clDefault.
  Result:
  - If the Bitmap parameter contains a bitmap other than 24 or 32bit the
    function returns False and GetLastError yields ERROR_INVALID_DATA
  - If the FillColor is invalid, the function returns False and
    GetLastError will yield a value of ERROR_INVALID_PARAMETER
  - Else the function will signal success by returning True

  If it is intended to use the function on other pixel format's for now,
  there's the only workaround of changing the pixel format of the bitmap
  to one of the supported values and change it back afterwards ...
  e.g.: Bitmap.PixelFormat:=pf24bit;

  [v1.01 - Last update: 2003-06-27]
  Assarbad AT gmx DOT info | http://assarbad.net | http://assarbad.org

  ----------------------------------------------------------------------
  History
  v1.01 [2003-06-27]
  - Fixed a bug with 24bit format which (as a side effect) increases
    speed for this pixel format. The old code always read 4 bytes
    instead of 3 - which read beyond the reserved memory and thus
    raised an exception!
  v1.00 [2003-06-22]
  - Initial public release

 ************************************************************************)
var
  format: TPixelFormat;
  pxsize, x, y: Integer;
  pszBmp: PChar;
begin
  result := False;
// Save pixel format (we read only once but use it multiple times)
  format := Bitmap.PixelFormat;
// Check if the input data is valid! Handle only 24 and 32 byte bitmaps
  case format of
// Set pixel size
    pf24Bit: pxsize := 3;
    pf32bit: pxsize := 4;
  else
    SetLastError(ERROR_INVALID_DATA); // Fehler ...
    exit; // ... und raus!
  end;
// Normalize the color value
  case FillColor of
// Standard Windows colors can be queried through the GetSysColor API!
    clScrollBar,
      clBackground,
      clActiveCaption,
      clInactiveCaption,
      clMenu,
      clWindow,
      clWindowFrame,
      clMenuText,
      clWindowText,
      clCaptionText,
      clActiveBorder,
      clInactiveBorder,
      clAppWorkSpace,
      clHighlight,
      clHighlightText,
      clBtnFace,
      clBtnShadow,
      clGrayText,
      clBtnText,
      clInactiveCaptionText,
      clBtnHighlight,
      cl3DDkShadow,
      cl3DLight,
      clInfoText,
      clInfoBk:
      FillColor := GetSysColor(FillColor and (not $80000000));
// Invalid color values ...
    clNone, // We don't fill none ...
      clDefault: // We don't know what's default!
      begin
        SetLastError(ERROR_INVALID_PARAMETER);
        exit;
      end;
  end;
// This case is obsolete for now ... but it will be needed if you extend the
// number of supported pixel formats!
  case format of
    pf24Bit:
// Do the job for full height
      for y := Bitmap.Height - 1 downto 0 do
// ... and full width
        for x := Bitmap.Width - 1 downto 0 do
        try
// Calculate offset of the DWORD to read
          pszBmp := PChar(Bitmap.ScanLine[y]) + x * pxsize;
          asm
// Save registers
            push  eax
            push  esi
// Actual routine
            mov   esi, [pszBmp];
//          Load fill color into eax
            mov   eax, FillColor
//          TColor and Bitmap in memory have different byte order -> swap bytes
            bswap eax
//          Write back into the memory position (byte by byte to not raise an exception)
            mov   [esi+0], ah
            shr   eax, 16
            mov   [esi+1], ax
// Restore registers
            pop   esi
            pop   eax
          end;
        except;
        end;
    pf32Bit:
// Do the job for full height
      for y := Bitmap.Height - 1 downto 0 do
// ... and full width
        for x := Bitmap.Width - 1 downto 0 do
        try
// Calculate offset of the DWORD to read
          pszBmp := PChar(Bitmap.ScanLine[y]) + x * pxsize;
          asm
// Save registers
            push  eax
            push  edx
            push  esi
// Actual routine
            mov   esi, [pszBmp];
//          Load color value (i.e. DWORD at pointer position) into edx
            mov   edx, [esi]
//          Save the upper byte (next pixel for 24bit, Alpha for 32bit)
            and   edx, $FF000000
//          Load fill color into eax
            mov   eax, FillColor
//          TColor and Bitmap in memory have different byte order -> swap bytes
            bswap eax
//          Now shift right by 8 bits because the important (previously lower)
//          3 bytes are now the 3 upper ones -> shift them back
//          At this point the upper byte is $00
            shr   eax, 8
//          Combine old upper byte and our fill color
            or    eax, edx
//          Write back into the memory position
            mov   [esi], eax
// Restore registers
            pop   esi
            pop   edx
            pop   eax
          end;
        except;
        end;
  end;
// Force update on the bitmap
  Bitmap.Modified := True;
  result := True;
end;

function ColorMix(Bitmap: TBitmap; FillColor: TColor): Boolean;
(************************************************************************
  This function is PUBLIC DOMAIN.

  The function takes a VCL TBitmap object and the FillColor (as TColor
  value) as parameters. There is the limitation, that the following
  color values are simply senseless and therefore unsupported: clNone and
  clDefault.
  Result:
  - If the Bitmap parameter contains a bitmap other than 24 or 32bit the
    function returns False and GetLastError yields ERROR_INVALID_DATA
  - If the FillColor is invalid, the function returns False and
    GetLastError will yield a value of ERROR_INVALID_PARAMETER
  - Else the function will signal success by returning True

  If it is intended to use the function on other pixel format's for now,
  there's the only workaround of changing the pixel format of the bitmap
  to one of the supported values and change it back afterwards ...
  e.g.: Bitmap.PixelFormat:=pf24bit;

  [v1.00 - Last update: 2003-06-27]
  Assarbad AT gmx DOT info | http://assarbad.net | http://assarbad.org

  ----------------------------------------------------------------------
  History
  v1.00 [2003-06-27]
  - Initial public release
  - Derived from ColorFill()

 ************************************************************************)
var
  format: TPixelFormat;
  pxsize, x, y: Integer;
  pszBmp: PChar;
begin
  result := False;
// Save pixel format (we read only once but use it multiple times)
  format := Bitmap.PixelFormat;
// Check if the input data is valid! Handle only 24 and 32 byte bitmaps
  case format of
// Set pixel size
    pf24Bit: pxsize := 3;
    pf32bit: pxsize := 4;
  else
    SetLastError(ERROR_INVALID_DATA); // Fehler ...
    exit; // ... und raus!
  end;
// Normalize the color value
  case FillColor of
// Standard Windows colors can be queried through the GetSysColor API!
    clScrollBar,
      clBackground,
      clActiveCaption,
      clInactiveCaption,
      clMenu,
      clWindow,
      clWindowFrame,
      clMenuText,
      clWindowText,
      clCaptionText,
      clActiveBorder,
      clInactiveBorder,
      clAppWorkSpace,
      clHighlight,
      clHighlightText,
      clBtnFace,
      clBtnShadow,
      clGrayText,
      clBtnText,
      clInactiveCaptionText,
      clBtnHighlight,
      cl3DDkShadow,
      cl3DLight,
      clInfoText,
      clInfoBk:
      FillColor := GetSysColor(FillColor and (not $80000000));
// Invalid color values ...
    clNone, // We don't fill none ...
      clDefault: // We don't know what's default!
      begin
        SetLastError(ERROR_INVALID_PARAMETER);
        exit;
      end;
  end;
// This case is obsolete for now ... but it will be needed if you extend the
// number of supported pixel formats!
  case format of
    pf24Bit:
// Do the job for full height
      for y := Bitmap.Height - 1 downto 0 do
// ... and full width
        for x := Bitmap.Width - 1 downto 0 do
        try
// Calculate offset of the DWORD to read
          pszBmp := PChar(Bitmap.ScanLine[y]) + x * pxsize;
          asm
// Save registers
            push  eax
            push  edx
            push  esi
// Actual routine
            mov   esi, [pszBmp];
//          Zero out edx
            xor   edx, edx
//          Copy original color value
            mov   dl, [esi+2]
            shl   edx, 16
            mov   dx, [esi+0]
//          Load fill color into eax
            mov   eax, FillColor
//          TColor and Bitmap in memory have different byte order -> swap bytes
            bswap eax
//          Upper byte in eax is zero after next instruction
            shr   eax, 8
//          Combine the both color values ...
            or    eax, edx
//          Write back into the memory position (byte by byte to not raise an exception)
            mov   [esi+0], ax
            shr   eax, 16
            mov   [esi+2], al
// Restore registers
            pop   esi
            push  edx
            pop   eax
          end;
        except;
        end;
    pf32Bit:
// Do the job for full height
      for y := Bitmap.Height - 1 downto 0 do
// ... and full width
        for x := Bitmap.Width - 1 downto 0 do
        try
// Calculate offset of the DWORD to read
          pszBmp := PChar(Bitmap.ScanLine[y]) + x * pxsize;
          asm
// Save registers
            push  eax
            push  edx
            push  esi
// Actual routine
            mov   esi, [pszBmp];
//          Load color value (i.e. DWORD at pointer position) into edx
            mov   edx, [esi]
//          Save the upper byte (next pixel for 24bit, Alpha for 32bit)
//            and   edx, $FF000000
//          Load fill color into eax
            mov   eax, FillColor
//          TColor and Bitmap in memory have different byte order -> swap bytes
            bswap eax
//          Now shift right by 8 bits because the important (previously lower)
//          3 bytes are now the 3 upper ones -> shift them back
//          At this point the upper byte is $00
            shr   eax, 8
//          Combine old upper byte and our fill color
            or    eax, edx
//          Write back into the memory position
            mov   [esi], eax
// Restore registers
            pop   esi
            pop   edx
            pop   eax
          end;
        except;
        end;
  end;
// Force update on the bitmap
  Bitmap.Modified := True;
  result := True;
end;