object Form10: TForm10
  Left = 0
  Top = 0
  Caption = 'Form10'
  ClientHeight = 341
  ClientWidth = 446
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Image1: TImage
    Left = 8
    Top = 8
    Width = 211
    Height = 296
  end
  object Image2: TImage
    Left = 225
    Top = 8
    Width = 211
    Height = 296
  end
  object Button1: TButton
    Left = 361
    Top = 310
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
end



unit Unit10;

interface

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

type
  TForm10 = class(TForm)
    Image1: TImage;
    Image2: TImage;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form10: TForm10;

implementation

{$R *.dfm}

function Translate(X, Y: Single): tagXFORM;
begin
  Result.eM11 := 1;
  Result.eM12 := 0;
  Result.eM21 := 0;
  Result.eM22 := 1;
  Result.eDx := X;
  Result.eDy := Y;
end;

function Stretch(X, Y: Single): tagXFORM;
begin
  Result.eM11 := X;
  Result.eM12 := 0;
  Result.eM21 := 0;
  Result.eM22 := Y;
  Result.eDx := 0;
  Result.eDy := 0;
end;

function R90: tagXFORM; { O= 0,0 }
begin
  Result.eM11 := 0;
  Result.eM12 := -1;
  Result.eM21 := 1;
  Result.eM22 := 0;
  Result.eDx := 0;
  Result.eDy := 0;
end;

function CombineTransform(x1, x2: tagXFORM): tagXFORM;
begin
  Result.eM11 := x1.eM11 * x2.eM11 + x1.eM12 * x2.eM21;
  Result.eM12 := x1.eM11 * x2.eM12 + x1.eM12 * x2.eM22;
  Result.eM21 := x1.eM21 * x2.eM11 + x1.eM22 * x2.eM21;
  Result.eM22 := x1.eM21 * x2.eM12 + x1.eM22 * x2.eM22;
  Result.eDx := x1.eDx * x2.eM11 + x1.eDy * x2.eM21 + x2.eDx;
  Result.eDy := x1.eDx * x2.eM12 + x1.eDy * x2.eM22 + x2.eDy;
end;

procedure TForm10.Button1Click(Sender: TObject);
var
  tr: tagXFORM;
  bm: TBitmap;
begin
  bm := TBitmap.Create;
  bm.Width := Image2.Width;
  bm.Height := Image2.Height;
  SetGraphicsMode(bm.Canvas.Handle, GM_ADVANCED);

  { Page 1 }
  tr := CombineTransform(R90, Stretch(210 / 297, 210 / 297));
  tr := CombineTransform(tr, Translate(0, bm.Height));
  SetWorldTransform(bm.Canvas.Handle, tr);
  BitBlt(bm.Canvas.Handle, 0, 0, bm.Width, bm.Height, Image1.Picture.Bitmap.Canvas.Handle, 0, 0, SRCCOPY);

  { Page 2 }
  tr := CombineTransform(R90, Stretch(210 / 297, 210 / 297));
  tr := CombineTransform(tr, Translate(0, bm.Height div 2)); { <- the only difference }
  SetWorldTransform(bm.Canvas.Handle, tr);
  BitBlt(bm.Canvas.Handle, 0, 0, bm.Width, bm.Height, Image1.Picture.Bitmap.Canvas.Handle, 0, 0, SRCCOPY);

  Image2.Picture.Bitmap.Assign(bm);
  bm.Free;
end;

end.