Чтобы преобразовать Icon в Bitmap используйте TImageList. для обратного преобразования замените метод AddIcon на Add, и метод GetBitmap на GetIcon.

function Icon2Bitmap(Icon: TIcon): TBitmap;
begin
with TImageList.Create (nil) do
begin
AddIcon (Icon);
Result := TBitmap.Create;
GetBitmap (0, Result);
Free;
end;
end;

procedure TIconShow.FileListBox1Click(Sender: TObject);
var

MyIcon: TIcon;
MyBitMap: TBitmap;
begin

MyIcon := TIcon.Create;
MyBitMap := TBitmap.Create;

try
{ получаем имя файла и связанную с ним иконку}
strFileName := FileListBox1.Items[FileListBox1.ItemIndex];
StrPCopy(cStrFileName, strFileName);
MyIcon.Handle := ExtractIcon(hInstance, cStrFileName, 0);

{ рисуем иконку на bitmap в speedbutton }
SpeedButton1.Glyph := MyBitMap;
SpeedButton1.Glyph.Width := MyIcon.Width;
SpeedButton1.Glyph.Height := MyIcon.Height;
SpeedButton1.Glyph.Canvas.Draw(0, 0, MyIcon);

SpeedButton1.Hint := strFileName;

finally
MyIcon.Free;
MyBitMap.Free;
end;
end;

function InvertBmp1(SourceBmp: TBitmap): TBitMap;
var
i, j: Longint;
tmp: TBitMap;
red, green, blue: Byte;
PixelColor: Longint;
begin
tmp := TBitmap.Create;
tmp.Width := SourceBmp.Width;
tmp.Height := SourceBmp.Height;
for i := 0 to SourceBmp.Width - 1 do
begin
for j := 0 to SourceBmp.Height - 1 do
begin
PixelColor := ColorToRGB(SourceBmp.Canvas.Pixels[i, j]);
red := PixelColor;
green := PixelColor shr 8;
blue := PixelColor shr 16;
red := 255 - red;
green := 255 - green;
blue := 255 - blue;
tmp.Canvas.pixels[i, j] := (red shl 8 + green) shl 8 + blue;
end;
end;
Result := tmp;
end;

function InvertBmp2(ABitmap : TBitmap) : TBitmap;
var
l_bmp : TBitmap;
begin
l_bmp := TBitmap.Create;
l_bmp.Width := ABitmap.Width;
l_bmp.Height := ABitmap.Height;
l_bmp.PixelFormat := ABitmap.PixelFormat;
BitBlt( l_bmp.Canvas.Handle, 0, 0, l_bmp.Width, l_bmp.Height,
ABitmap.Canvas.Handle, 0, 0, SRCINVERT );
result := l_bmp;
end;

{
Dieses ist eine ziemlich schnelle Methode, eine Farbumkehrung auf einem
Bitmap anzuwenden.
}

{
This is a very fast method to invert the colors of a bitmap.
}

function InvertBitmap(MyBitmap: TBitmap): TBitmap;
var
x, y: Integer;
ByteArray: PByteArray;
begin
MyBitmap.PixelFormat := pf24Bit;
for y := 0 to MyBitmap.Height - 1 do
begin
ByteArray := MyBitmap.ScanLine[y];
for x := 0 to MyBitmap.Width * 3 - 1 do
begin
ByteArray[x] := 255 - ByteArray[x];
end;
end;
Result := MyBitmap;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
Image1.Picture.Bitmap := InvertBitmap(Image1.Picture.Bitmap);
Image1.Refresh;
end;

procedure loadgraphic(naam:string);
var
HResInfo: THandle;
BMF: TBitmapFileHeader;
MemHandle: THandle;
Stream: TMemoryStream;
ResPtr: PByte;
ResSize: Longint;
null:array [0..8] of char;
begin
strpcopy (null, naam);
HResInfo := FindResource(HInstance, null, RT_Bitmap);
ResSize := SizeofResource(HInstance, HResInfo);
MemHandle := LoadResource(HInstance, HResInfo);
ResPtr := LockResource(MemHandle);
Stream := TMemoryStream.Create;
try
Stream.SetSize(ResSize + SizeOf(BMF));
BMF.bfType := $4D42;
Stream.write(BMF, SizeOf(BMF));
Stream.write(ResPtr^, ResSize);
Stream.Seek(0, 0);
Bitmap:=tbitmap.create;
Bitmap.LoadFromStream(Stream);
finally
Stream.Free;
end;
FreeResource(MemHandle);
end;