unit UThreads;

interface

uses
  Classes, ExtCtrls, Windows;

type
  TFarbe = record
    R : Integer;
    G : Integer;
    B : Integer;
  end;

type
  TMyThread = class (TThread)
  private
    FImage : TImage;
  public

  protected
    procedure Execute(); override;
  published
    property Image : TImage Read FImage Write FImage;
  end;

implementation

procedure TMyThread.Execute();
  var x, y : Integer;
      Farbe : TFarbe;
begin
  for x:=0 to FImage.Width do
    begin
      for y:=0 to FImage.Height do
        begin
          Randomize;
          with Farbe do
            begin
              R:=Random(255);
              G:=Random(255);
              B:=Random(255);

              FImage.Canvas.Pixels[x, y]:=RGB(R, G, B);
            end;
        end;
    end;
end;

end.

procedure TForm1.Button1Click(Sender: TObject);
  var MyThread1 : TMyThread;
      MyThread2 : TMyThread;
      MyThread3 : TMyThread;
      MyThread4 : TMyThread;
begin
  MyThread1:=TMyThread.Create(True);
  MyThread2:=TMyThread.Create(True);
  MyThread3:=TMyThread.Create(True);
  MyThread4:=TMyThread.Create(True);
  MyThread1.Image:=Image1;
  MyThread2.Image:=Image2;
  MyThread3.Image:=Image3;
  MyThread4.Image:=Image4;
  MyThread1.Resume;
  MyThread2.Resume;
  MyThread3.Resume;
  MyThread4.Resume;
end;