Send/receive an JPEG image

It most likely is. Better close the connection first (after checking if it's done of course) and only then free the memory.
Not sure, but you may have to close the stream as well (don't have Delphi on this computer).

I have tryed to remove the line MyStream.Free...But the same error keeps popping up...

from the TNMUDP help:

create the Stream before the try/finally...

if you have an OnInvalidHost:
When the OnInvalidHost event is called, the InputQuery function (function in delphi OnInvalidHost example)  is called, allowing the user to input a new host name to replace the invalid one previously entered. If the user clicks the Ok Button, the handled parameter is set to TRUE, and the component attempts it's action again with the new hostname. If the hostname is still invalid, or the cancel button was clicked in the dialog, an exception is raised.

the Delphi Help example:
 procedure TForm1.Button1Click(Sender: TObject);
var
  MyStream: TMemoryStream;
  C: String;
begin
  C := Edit1.Text;
  NMUDP1.RemoteHost := '127.0.0.1';
  NMUDP1.ReportLevel := Status_Basic;
  NMUDP1.RemotePort := 6668;
  MyStream := TMemoryStream.Create;
  try
    MyStream.Write(C[1], Length(C));
    NMUDP1.SendStream(MyStream);
  finally
    MyStream.Free;
  end;
end;

When Button1 is clicked, the text in Edit1 is written into the stream MyStream. The SendStream method is used to send the stream to the remote host, which is 127.0.0.1 (local host) in this instance. Note that MyStream is utilized within a try...finally loop to prevent a memory leak.

I have looked at the example, but  I think MyStream.Write only works if it is an integer... I Have tried  to replace the line MyStream.Write(C[1], Length(C)); with MyStream.Write(Jpg[1], Length(Jpg)); But this does not work...

of course, that's an example about sending strings...

my post was about the freeing on finally, and that's ok in your source too...the difference is in the stream creation (before the try...finally) and if you're passing some code to the OnInvalidHost event setting Handle to true, but the Host is not valid, this raises an exception...

Hi,

The code below works fine with very small pictures but not with bigger ones:
There are one NMUDP, one Button and two Image components on a form. Image1 has a small bmp loaded in design-time and Image2 is empty. When you press the button, the picture from Image1 is being transferred via NMUDP and assigned to Image2.
------
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, NMUDP, ExtCtrls;

type
  TForm1 = class(TForm)
    Image1: TImage;
    Image2: TImage;
    NMUDP1: TNMUDP;
    Button1: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure NMUDP1DataReceived(Sender: TComponent; NumberBytes: Integer;
      FromIP: String; Port: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

uses jpeg;

procedure TForm1.FormCreate(Sender: TObject);
begin
  NMUDP1.RemoteHost := '127.0.0.1';
  NMUDP1.ReportLevel := Status_Basic;
  NMUDP1.LocalPort := 6668;
  NMUDP1.RemotePort := 6668;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
 MyStream: TMemoryStream;
 Jpg: TJPEGImage;
begin
 //Create a JPEG image and assign the loaded picture
 Jpg := TJPEGImage.Create;
 Jpg.Assign(Image1.Picture.Graphic);
 try
  // Create a stream and save the image to the stream
   MyStream := TMemoryStream.Create;
   try
     Jpg.SaveToStream(MyStream);
     NMUDP1.SendStream(MyStream);
   finally
     MyStream.Free;
   end;
 finally
   Jpg.Free;
 end;
end;

procedure TForm1.NMUDP1DataReceived(Sender: TComponent;
  NumberBytes: Integer; FromIP: String; Port: Integer);
var
  MyStream: TMemoryStream;
  Jpg: TJPEGImage;
begin
 try
  Jpg := TJPEGImage.Create;
  try
    MyStream := TMemoryStream.Create;
    try
      NMUDP1.ReadStream(MyStream);
      MyStream.Position := 0;
      Jpg.LoadFromStream(MyStream);
      Image2.Picture.Assign(jpg);
    finally
      MyStream.Free;
    end;
  finally
    Jpg.Free;
  end;
 except
 end;
end;

end.
-------
Regards, Geo

OnDataReceived event should be:

procedure TForm1.NMUDP1DataReceived(Sender: TComponent;
  NumberBytes: Integer; FromIP: String; Port: Integer);
var
  MyStream: TMemoryStream;
  Jpg: TJPEGImage;
begin
  Jpg := TJPEGImage.Create;
  try
    MyStream := TMemoryStream.Create;
    try
      NMUDP1.ReadStream(MyStream);
      Jpg.LoadFromStream(MyStream);
      Image2.Picture.Assign(jpg);
      MyStream.Clear;
    finally
      MyStream.Free;
    end;
  finally
    Jpg.Free;
  end;
end;

Regards, Geo

Thanks Geo... I tried my original code with a small bimap and it works just fine... I just don´t see why it won´t work with a larger JPEG image.... I will give it some time to see if anyone can solve it...

Hmm... You´r probably right....

Take a look at http://community.borland.com/article/0,1410,20378,00.html
The article come with a sample project.

Anyone have an idea on how to cut the stream into small pieces, send them one after another and assemble the picture on receipt?

Tango42:

If you are using Indy, then you do not have to worry about the packet size; because it takes care of that for you

Regarding your original error; most likely; you are getting the error because you are not converting the jpg correctly.
here is your original code after adding three more lines to it.


procedure TTransmitterForm.btnTransmitClick(Sender: TObject);
var
 MyStream: TMemoryStream;
 Jpg: TJPEGImage;
begin
 NMUDP.RemoteHost := Edit1.Text;
 NMUDP.RemotePort := StrToInt(Edit2.Text);
 //Create a JPEG image and assign the loaded picture
 Jpg := TJPEGImage.Create;
 Jpg.Assign(Image.Picture);
 try

      JPG.CompressionQuality := 50;  // or whatever you need
      JPG.JPEGNeeded;
      JPG.Compress;

  // Create a stream and save the image to the stream
   MyStream := TMemoryStream.Create;
   Jpg.SaveToStream(MyStream);
   MyStream.Position := 0;
   NMUDP.SendStream(MyStream);
 finally
   MyStream.Free;
   Jpg.Free;
 end;
end;