uses pngimage;    {从 png 图片到十六进制字符串}  function Png2Hex(png: TPngImage): string;  var    stream: TMemoryStream;  begin    stream := TMemoryStream.Create;    png.SaveToStream(stream);    SetLength(Result, stream.Size * 2);    BinToHex(stream.Memory, PChar(Result), stream.Size);    stream.Free;  end;    {从十六进制字符串恢复 png 图片}  procedure Hex2Png(str: string; out png: TPngImage);  var    stream: TMemoryStream;  begin    if not Assigned(png) then png := TPngImage.Create;    stream := TMemoryStream.Create;    stream.SetSize(Length(str) div 2);    HexToBin(PChar(str), stream.Memory, stream.Size);    png.LoadFromStream(stream);    stream.Free;  end;    {测试}  procedure TForm1.Button1Click(Sender: TObject);  var    png: TPngImage;  begin    png := TPngImage.Create;    png.LoadFromFile(‘c:/temp/test.png‘);    Memo1.Text := Png2Hex(png);    png.Free;  end;    procedure TForm1.Button2Click(Sender: TObject);  var    png: TPngImage;  begin    png := TPngImage.Create;    Hex2Png(Memo1.Text, png);    Canvas.Draw(0, 0, png);    png.Free;  end;