Save an image and other data to a file in delphi

I have an image, a string, and an integer that i need to save/read as a file. What would be the best way to do this. I was thinking a TStream, but I am unsure of how to implement it.

You could use Delphi's built-in component streaming support and save it either as binary or text data. One disadvantage with this method is if your images are high-resolution then you might be punished in greater file-size when dumping the in-memory-pixel-data to disk compared to the image's original file-format, e.g. jpeg. In my example below I derive a class from TImage and add a string value, MyString and an integer, MyInteger and save as binary data.

Stream Component to/from a binary-file

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls;

type
  TMyImage = class(TImage)
  private
    FString : string;
    FInteger : integer;
  public

  published
    property MyString: string read FString write FString;
    property MyInteger: Integer read FInteger write FInteger;
  end;

  TFormMain = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    FMyImage : TMyImage;
    FMyImage2 : TMyImage;
  public

  end;

var
  FormMain: TFormMain;

implementation

{$R *.dfm}    

procedure WriteComponent(Component: TComponent; Filename : String);
var
  m :TMemoryStream;    
begin
  m := TMemoryStream.Create;
  try
    m.WriteComponent(Component);
    m.Seek(0, soFromBeginning);
    m.SaveToFile(Filename);
  finally
    m.Free;
  end;
end;

function ReadComponent(Filename : String): TComponent;
var
  m :TMemoryStream;    
begin
  m := TMemoryStream.Create;
  try
    m.LoadFromFile(FileName);
    m.Seek(0, soFromBeginning);
    result := m.ReadComponent(nil);
  finally
    m.Free;
  end;
end;

procedure TFormMain.FormCreate(Sender: TObject);
begin
  FMyImage := TMyImage.Create(Self);

  FMyImage.Picture.LoadFromFile('C:\...\Delphi\Common Images\ALIGNPAL.BMP');
  FMyImage.MyString := 'Hello World';
  FMyImage.MyInteger := 12345;

  WriteComponent(FMyImage, 'c:\test.dat');
  FMyImage2 := ReadComponent('c:\test.dat') as TMyImage;
end;

initialization

 RegisterClass(TMyImage);

end.

A simplified approach

If you want to get by with only one String and one Integer than you could use TImage's Caption and Tag properties.

...
FImage : TImage;
FImage2 : TImage;
....

procedure TFormMain.FormCreate(Sender: TObject);
begin
  FImage := TImage.Create(Self);

  FImage.Picture.LoadFromFile('C:\...\Delphi\Common Images\ALIGNPAL.BMP');
  FImage.Caption := 'Hello World';
  FImage.Tag := 12345;

  WriteComponent(FImage, 'c:\test.dat');

  FImage2 := ReadComponent('c:\test.dat') as TImage;
end;

Stream Component to/from text

Below I'v also added useful helper functions, found here, if you want more "readable" data-files by making string representations of the binary-data. File size will however increase.

function StringToComponentProc(Value: string): TComponent;
var
  StrStream:TStringStream;
  BinStream: TMemoryStream;
begin
  StrStream := TStringStream.Create(Value);
  try
    BinStream := TMemoryStream.Create;
    try
      ObjectTextToBinary(StrStream, BinStream);
      BinStream.Seek(0, soFromBeginning);
      Result:= BinStream.ReadComponent(nil);
    finally
      BinStream.Free;
    end;
  finally
    StrStream.Free;
  end;
end;

function ComponentToStringProc(Component: TComponent): string;
var
  BinStream:TMemoryStream;
  StrStream: TStringStream;
  s: string;
begin
  BinStream := TMemoryStream.Create;
  try
    StrStream := TStringStream.Create(s);
    try
      BinStream.WriteComponent(Component);
      BinStream.Seek(0, soFromBeginning);
      ObjectBinaryToText(BinStream, StrStream);
      StrStream.Seek(0, soFromBeginning);
      Result:= StrStream.DataString;
    finally
      StrStream.Free;
    end;
  finally
    BinStream.Free
  end;
end;