function CutImgToBase(fn: string): string;  // 压缩图片只能压缩bmp：将jpg转换成bmp再压缩

var

	m1: TMemoryStream;

	m2: TStringStream;

	jpg: TJPEGImage;

	bmp: TBitmap;

begin

	jpg := TJpegImage.Create;

	bmp := TBitmap.Create;

  m1 := TMemoryStream.Create;

  m2 := TStringStream.Create;

	jpg.LoadFromFile(fn);

	bmp.Width := jpg.Width div 2;

	bmp.Height := jpg.Height div 2;

	bmp.Canvas.StretchDraw(bmp.Canvas.ClipRect, jpg);

	jpg.Assign(bmp);

	jpg.CompressionQuality := 30;

	jpg.Compress;										// 先指定大小再压缩

	jpg.SaveToStream(m1);

	m1.Position := 0;               // 一定要还原指针，才能base64

	EncdDecd.EncodeStream(m1, m2);

	result := m2.DataString.Replace(#13, '').Replace(#10, '');

	bmp.Free;

	jpg.Free;

  m1.Free;

	m2.Free;

end;

procedure TForm2.Button4Click(Sender: TObject);   // 调用函数  压缩并编码

var

	m: TStringStream;

	s: string;

begin

	s := CutImgToBase('test.jpg');

	FilePutContents('mm.txt', s);

	m := TStringStream.Create(s);

	Memo1.Lines.Add(m.DataString);

	m.SaveToFile('base64.txt');

end;

procedure TForm2.DecodeBaseClick(Sender: TObject);   // 解码

var

	m1: TStringStream;

	m2: TMemoryStream;

begin

	m1 := TStringStream.Create;

	m2 := TMemoryStream.Create;

	m1.LoadFromFile('base64.txt');

	EncdDecd.DecodeStream(m1, m2);

	m2.SaveToFile('1.jpg');

	m1.Free;

	m2.Free;

end;