二进制文件转成文本保存，并可以读回

以 JPEG 图片为例，以下代码演示了如何将一个 JPEG 图片保存为纯文本形式，并将其以图片形式读回并显示。
保存 TXT：

function TForm1.JpegToText(AFileName:string; SaveFile: Boolean; TxtFileName: string): string;
var
FileStream        : TFileStream;
StringStream      : TStringStream;
FSize             : integer;
FileData          : string;
i                 : integer;
DataStr           : string;
begin
try
    FileStream := TFileStream.Create(OpenDialog1.FileName, fmOpenRead);
    StringStream := TStringStream.Create(EmptyStr);
    FSize := FileStream.Size;
    StringStream.CopyFrom(FileStream, FSize);
    FileData := StringStream.DataString;
    DataStr := EmptyStr;
    for i := 1 to Length(FileData) do
    begin
      DataStr := DataStr + InttoHex(Ord(FileData[i]), 2);
    end;
    Result := DataStr;
    if SaveFile then
    begin
      with TStringList.Create do
      begin
        Text := DataStr;
        SaveToFile(TxtFileName);
        Free;
      end; 
    end; 
finally
    freeandnil(FileStream);
    freeandnil(StringStream);
end;
end;

从 TXT 读回 JPEG：

function TForm1.TextToJpeg(AFileName: string; SaveFile: Boolean; JpegFileName: string): TJPEGImage;
var
buf               : array of Byte;
DataLength        : Integer;
i                 : Integer;
DataStr           : string;
ByteFile          : file of byte;
jpg               : TJPEGImage;
tmpFileName: string;
begin
with TStringList.Create do
begin
    LoadFromFile(AFileName);
    DataStr := Text;
    Free;
end;
DataLength := Length(DataStr) div 2-1;
SetLength(buf, DataLength);
for i := 1 to DataLength do
begin
    buf[i - 1] := StrToInt('$' + copy(DataStr, (i - 1) * 2 + 1, 2));
end;
tmpFileName := ExtractFilePath(ParamStr(0))+'tmp.jpg';
AssignFile(ByteFile, tmpFileName);
Rewrite(ByteFile);
for i := 0 to DataLength - 1 do
begin
    write(ByteFile, buf[i]);
end;
CloseFile(ByteFile);
Result := TJPEGImage.Create;
Result.LoadFromFile(tmpFileName);
if SaveFile then
    Result.SaveToFile(JpegFileName);
DeleteFile(tmpFileName);
end;