unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, ExtDlgs, jpeg;

type
  TForm1 = class(TForm)
    OpenPictureDialog1: TOpenPictureDialog;
    Image1: TImage;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormResize(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
openfilepath:string;
begin
openpicturedialog1.Filter:= '全部 (*.jpg;*.jpeg;*.bmp;*.ico;*.emf;*.wmf;*.png)|*.jpg;*.jpeg;*.bmp;*.i' +
      'co;*.emf;*.wmf;*.png|JPEG 图像文件 (*.jpg)|*.jpg|JPEG 图像文件 (*.jpeg)|*.jpeg' +
      '|位图 (*.bmp)|*.bmp|图标 (*.ico)|*.ico|增强图元文件 (*.emf)|*.emf|图元文件 (*.' +
      'wmf)|*.wmf|可移植图片(*.png)|*.png';
    if openpicturedialog1.Execute then
    begin
        openfilepath:=openpictureDialog1.FileName;
        image1.Picture.LoadFromFile(openfilepath);
        image1.AutoSize:=false;
        image1.Stretch:=true;
    end;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
//Image1.Width:=form1.ClientWidth+10;
//Image1.Height:=form1.ClientHeight+10;
end;

end.

源代码