delphi 从 TWebbrowse组件中获取图片

unit Unit1;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, OleCtrls, SHDocVw, MSHtml;
type
  // 此定义是从 XE8 的 MSHTML 单元中抄的
  IHTMLElementRender = interface(IUnknown)
    [‘{3050F669-98B5-11CF-BB82-00AA00BDCE0B}‘]
    function DrawToDC(hdc: hdc): HResult; stdcall;
    function SetDocumentPrinter(const bstrPrinterName: WideString; hdc: hdc): HResult; stdcall;
  end;

  TForm1 = class(TForm)
    WebBrowser1: TWebBrowser;
    Image1: TImage;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FormShow(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    FFirstShow: Boolean;
    FCodeBmp: TBitmap;
  end;

var
  Form1: TForm1;

implementation
const
  csUrl = ‘https://account.guokr.com/sign_in/?‘;
{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  FFirstShow := true;
  FCodeBmp := TBitmap.Create;
  FCodeBmp.Height := 40;
  FCodeBmp.Width := 100;
  FCodeBmp.PixelFormat := pf24bit;
end;

procedure TForm1.FormShow(Sender: TObject);
begin
 // 做一个 FirstOnShow 功能。
 // OnCreate 事件中使用 WebBrowser1.Navigate 的话，会出错的。
  if FFirstShow then
  begin
    WebBrowser1.Navigate(csUrl);
    FFirstShow := false;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Doc: IHTMLDocument2;
  Render: IHTMLElementRender;
begin
  Doc := WebBrowser1.Document as IHTMLDocument2;
  Render := Doc.All.Item(‘captchaImage‘, EmptyParam) as IHTMLElementRender;
  Render.DrawToDC(Self.Canvas.Handle);
  Render.DrawToDC(FCodeBmp.Canvas.Handle);
  Image1.Picture.Assign(FCodeBmp);
end;

end.