Paint a TBitmap in disabled state

Problem/Question/Abstract:

How can I make an image to appear enabled and disabled (i.e going from original to disabled-grey and back)? I know that TImage doesn't support this feature, so how would I implement this?

Answer:

Everyone from you saw that standard TSpeedButton allow to show a loaded glyph in "disabled" state when your original glyph will be converted into gray-scheme.

Sometimes to create similar bitmap is useful not only for TSpeedButton.

You can use the next my CreateDisabledBitmap procedure where such "disabled" bitmap (Destination parameter) will be created from your original bitmap (Source).

procedure CreateDisabledBitmap(Source, Destination: TBitmap);
const
  ROP_DSPDxax = $00E20746;
var
  DDB, MonoBmp: TBitmap;
  IWidth, IHeight: Integer;
  IRect: TRect;
begin
  IWidth := Source.Width;
  IHeight := Source.Height;
  Destination.Width := IWidth;
  Destination.Height := IHeight;
  IRect := Rect(0, 0, IWidth, IHeight);
  Destination.Canvas.Brush.Color := clBtnFace;
  Destination.Palette := CopyPalette(Source.Palette);
  MonoBmp := nil;
  DDB := nil;
  try
    MonoBmp := TBitmap.Create;
    DDB := TBitmap.Create;
    DDB.Assign(Source);
    DDB.HandleType := bmDDB;
    { Create a disabled version }
    with MonoBmp do
    begin
      Assign(Source);
      HandleType := bmDDB;
      Canvas.Brush.Color := clBlack;
      Width := IWidth;
      if Monochrome then
      begin
        Canvas.Font.Color := clWhite;
        Monochrome := False;
        Canvas.Brush.Color := clWhite;
      end;
      Monochrome := True;
    end;
    with Destination.Canvas do
    begin
      Brush.Color := clBtnFace;
      FillRect(IRect);
      Brush.Color := clBtnHighlight;
      SetTextColor(Handle, clBlack);
      SetBkColor(Handle, clWhite);
      BitBlt(Handle, 1, 1, IWidth, IHeight, MonoBmp.Canvas.Handle, 0, 0, ROP_DSPDxax);
      Brush.Color := clBtnShadow;
      SetTextColor(Handle, clBlack);
      SetBkColor(Handle, clWhite);
      BitBlt(Handle, 0, 0, IWidth, IHeight, MonoBmp.Canvas.Handle, 0, 0, ROP_DSPDxax);
    end;
  finally
    DDB.Free;
    MonoBmp.Free;
  end;
  Source.Dormant;
end;

Sample of use:

procedure TfrmMain.ButtonClick(Sender: TObject);
var
  Destination: TBitmap;
begin
  Destination := TBitmap.Create;
  try
    CreateDisabledBitmap(Image1.Picture.Bitmap, Destination);
    Image2.Picture.Bitmap.Assign(Destination);
  finally
    Destination.Free
  end
end;

where Image1 is TImage where you have an original bitmap and TImage2 will a container for created disabled bitmap.