Taking screenshot behind the form using magnification

[victorlus]

I am trying to capture screen behind form, photo that was capture is black someone has a solution?

https://i.imgur.com/lBO4I3J.png

Delphi-Quellcode:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    Initialized: BOOL;
    magWindowRect: TRect;
    hwndMag: HWND;
    HandleToMagnifier: HWND;
    function MyCreateDIBSection(DC: HDC; Width, Height: integer; BitCount: integer): HBITMAP;
    procedure DrawMagnifier(Width, Height: Integer);
    procedure RefreshMagnifier(rc:TRect);
   // procedure ResizeMagnifier;
    procedure InitializeMagnifier;
  public
    { Public declarations }
  end;


const
  MagFactor = 2.0;

var
  Form1: TForm1;


implementation

{$R *.dfm}


function TForm1.MyCreateDIBSection(DC: HDC; Width, Height, BitCount: integer): HBITMAP;
var
  lpbmi: TBitmapInfo;
  P: Pointer;
  AbITmAP : hbitmap;
  db : tbitmap;

begin

  Fillchar(lpbmi,  SizeOf(TBitmapInfo), 0);
  lpbmi.bmiHeader.biSize := sizeof(lpbmi.bmiHeader);
  lpbmi.bmiHeader.biHeight := - Height;
  lpbmi.bmiHeader.biWidth := width;
  lpbmi.bmiHeader.biPlanes := 1;
  lpbmi.bmiHeader.biBitCount := BitCount;
  lpbmi.bmiHeader.biCompression := BI_RGB;

  Result := CreateDIBSection(DC, lpbmi, DIB_RGB_COLORS, P, 0, 0);
end;

procedure TForm1.DrawMagnifier(Width, Height: Integer);
var
  aBitmap: HBITMAP;
  DC: HDC;
  bmp: TBitmap;
begin

  DC := GetWindowDC(HwndMag);
  bmp := TBitmap.Create;
  aBitmap := 0;
  try
    aBitmap := Form1.MyCreateDIBSection(DC, Width, Height, 32);
    SelectObject(DC, aBitmap);
    bmp.Handle := aBitmap;
    bmp.SaveToFile('Screen.bmp');
  finally
    DeleteObject(aBitmap);
    DeleteDC(DC);
    bmp.Free;
  end;
end;

procedure TForm1.RefreshMagnifier(rc: TRect);
begin

  MagSetWindowSource(hwndMag, rc);
  SetWindowPos(Handle, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);

  InvalidateRect(hwndMag, rc, true);
end;


procedure TForm1.InitializeMagnifier;
var
  matrix: TMagTransform;
    desktop : hwnd;
  desktoprect, sourceRect: TRect;
  filterList: THWNDArray;
  m_ScreenX, m_ScreenY, m_ScreenT, m_ScreenL: Integer;
begin

   desktop := GetDesktopWindow;
  GetWindowRect(desktop, desktoprect);

  m_ScreenT := desktoprect.Top;
  m_ScreenL := desktoprect.Left;
  m_ScreenX := desktoprect.right;
  m_ScreenY := desktoprect.bottom;

  hwndMag := CreateWindow(WC_MAGNIFIER, 'MagnifierWindow',
    WS_CHILD or MS_SHOWMAGNIFIEDCURSOR, 0, 0, m_ScreenX,
    m_ScreenY, Form1.handle, 0, hInstance, nil);

  if hwndMag = 0 then
    close;

  FillChar(matrix, Sizeof(matrix), 0);
  matrix.v[0][0] := MagFactor;
  matrix.v[1][1] := MagFactor;
  matrix.v[2][2] := 1.0;
  if MagSetWindowTransform(hWndMag, matrix) then
//    tmr1.Enabled := true;
end;



procedure MagScreenShot;
var
  desktop : hwnd;
  desktoprect, sourceRect: TRect;
  filterList: THWNDArray;
  m_ScreenX, m_ScreenY, m_ScreenT, m_ScreenL: Integer;
begin

  Form1.WindowState := wsMaximized;

  desktop := GetDesktopWindow;
  GetWindowRect(desktop, desktoprect);

  Form1.DrawMagnifier(desktoprect.Right, desktoprect.Bottom);
  Form1.RefreshMagnifier(desktoprect);

end;


procedure TForm1.Button1Click(Sender: TObject);
begin
  MagScreenShot;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin

 Initialized := MagInitialize;
  if not Initialized then
  begin
    Application.MessageBox('Init magnification failed', 'Error',
      mb_Ok + mb_IconError);
    close;
  end;

  InitializeMagnifier;


end;


procedure TForm1.FormDestroy(Sender: TObject);
begin
  if (initialized) then
    MagUninitialize;
end;

end.