Convert Bitmap to PNG

uses PNGImage

procedure BitmapFileToPNG(const Source, Dest: String);
var
  Bitmap: TBitmap;
  PNG: TPNGObject;
begin
  Bitmap := TBitmap.Create;
  PNG := TPNGObject.Create;
  try
    Bitmap.LoadFromFile(Source);
    PNG.TransparentColor := clBlack;  // Trz Farbe
    PNG.Transparent := true;          // Tranzparent
    PNG.Assign(Bitmap);
    PNG.SaveToFile(Dest);
  finally
    Bitmap.Free;
    PNG.Free;
  end
end;

Beispiel :

procedure TForm1.Button1Click(Sender: TObject);
begin
  if OpenDialog1.Execute then
  begin
    try
    BitmapFileToPNG(OpenDialog1.FileName, OpenDialog1.FileName + '.png');
    finally
    end;
  end;
end;

Download : PNGImage.pas