unit UCatchScreenShow;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls;

type
  TCatchScreenShowForm = class(TForm)
    ChildImage: TImage;
    ChildTimer: TTimer;
    procedure ChildTimerTimer(Sender: TObject);
    procedure ChildImageMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure ChildImageMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure FormShow(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  CatchScreenShowForm: TCatchScreenShowForm;
  foldx,x1,y1,x2,y2,oldx,oldy,foldy : Integer;
  Flag,Trace : Boolean;
implementation

uses MainForm, left;

{$R *.DFM}

procedure TCatchScreenShowForm.ChildTimerTimer(Sender: TObject);
var
  Fullscreen:Tbitmap;
  FullscreenCanvas:TCanvas;
  DC:HDC;
begin
  ChildTimer.Enabled := False;
  Fullscreen := TBitmap.Create;
  Fullscreen.Width := Screen.width;
  Fullscreen.Height := Screen.Height;
  DC:=GetDC(0);
  FullscreenCanvas := TCanvas.Create;
  FullscreenCanvas.Handle := DC;
  Fullscreen.Canvas.CopyRect(Rect(0,0,Screen.Width,Screen.Height),FullscreenCanvas,
  Rect(0,0,Screen.Width,Screen.Height));
  FullscreenCanvas.Free;
  ReleaseDC(0,DC);
  ChildImage.picture.Bitmap:=fullscreen;
  ChildImage.Width := Fullscreen.Width;
  ChildImage.Height:=Fullscreen.Height;
  Fullscreen.free;
  CatchScreenShowForm.WindowState := wsMaximized;
  CatchScreenShowForm.show;
  messagebeep(1);
  foldx:=-1;
  foldy:=-1;
  ChildImage.Canvas.Pen.mode := Pmnot; //筆的模式為取反
  ChildImage.Canvas.pen.color := clblack; //筆為黑色
  ChildImage.Canvas.brush.Style := bsclear;//空白刷子
  Flag := True;
end;


procedure TCatchScreenShowForm.ChildImageMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if trace=true then//是否在追蹤鼠標？
  begin//是，擦除舊的矩形并畫上新的矩形
    with ChildImage.canvas do
    begin
        rectangle(x1,y1,oldx,oldy);
        Rectangle(x1,y1,x,y);
        oldx:=x;
        oldy:=y;
    end;
  end
  else if flag=true then//在鼠標所在的位置上畫十字
  begin
    with ChildImage.canvas do
        begin
          MoveTo(foldx,0);//擦除舊的十字
          LineTo(foldx,Screen.Height);
          MoveTo(0,foldy);
          LineTo(Screen.Width,foldy);
          MoveTo(x,0);//畫上新的十字
          LineTo(x,Screen.Height);
          MoveTo(0,y);
          LineTo(Screen.Width,y);
          foldx:=x;
          foldy:=y;
        end;
  end;
end;

procedure TCatchScreenShowForm.ChildImageMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  Width,Height : Integer;
  NewBitmap : TBitmap;
begin
  if (Trace = False) then//TRACE表示是否在追蹤鼠標
  begin//首次點擊鼠標左鍵，開始追蹤鼠標。
    Flag := False;
    with ChildImage.canvas do
    begin
        MoveTo(foldx,0);
        LineTo(foldx,screen.height);
        MoveTo(0,foldy);
        LineTo(screen.width,foldy);
    end;
    x1 := x;
    y1 := y;
    oldx := x;
    oldy := y;
    Trace := True;
    ChildImage.Canvas.Pen.mode:=pmnot;//筆的模式為取反
    //這樣再在原處畫一遍矩形，相當于擦除矩形。
    ChildImage.canvas.pen.color := clblack;//筆為黑色
    ChildImage.canvas.brush.Style := bsclear;//空白刷子
    end
  else
  begin//第二次點擊，表示已經得到矩形了，把它拷貝到FORM1中的IMAGE部件上。
    x2 := x;
    y2 := y;
    Trace := False;
    ChildImage.Canvas.Rectangle(x1,y1,oldx,oldy);
    Width := abs(x2-x1);
    Height := abs(y2-y1);
    form1.image1.Width := Width;
    form1.image1.Height := Height;

    NewBitmap:=Tbitmap.create;
    NewBitmap.Width := Width;
    NewBitmap.Height := Height;
    NewBitmap.Canvas.CopyRect
    (Rect(0,0,width,Height),CatchScreenShowForm.ChildImage.Canvas,
    Rect(x1,y1,x2,y2));//拷貝
    form1.Image1.Picture.Bitmap := NewBitmap;//放到CatchScreenForm的ShowImage上
    NewBitmap.Free;
    CatchScreenShowForm.Hide;
    form1.Show;
    form1.WindowState := wsMaximized;
end;
end;

procedure TCatchScreenShowForm.FormClose(Sender: TObject;
  var Action: TCloseAction);
begin
  Action := caFree;
end;

procedure TCatchScreenShowForm.FormShow(Sender: TObject);
begin
  self.DoubleBuffered := true;
end;

end.