再学 GDI+[12]: 准备工作 - 矩形命中

本例效果图:

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代码文件:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs;



type

  TForm1 = class(TForm)

    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);

    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

    procedure FormPaint(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



var

  f: Boolean;

  x1,y1,x2,y2: Integer;

  RectArr: array of TRect;



procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  f := True;

  x1 := X;

  y1 := Y;

  x2 := X;

  y2 := Y;

end;



procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

  Y: Integer);

var

  i: Integer;

begin

  if f then

  begin

    Canvas.DrawFocusRect(Rect(x1,y1,x2,y2));

    x2 := X;

    y2 := Y;

    Canvas.DrawFocusRect(Rect(x1,y1,x2,y2));

  end else begin

    Text := '';

    for i := Low(RectArr) to High(RectArr) do

      if PtInRect(RectArr[i], Point(X,Y)) then

        Text := Format('在第 %d 个矩形中', [i+1]);

  end;

end;



procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  if not f then Exit;

  SetLength(RectArr, Length(RectArr)+1);

  RectArr[High(RectArr)] := Rect(x1,y1,x2,y2);

  f := False;

  Repaint;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  i: Integer;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  p := TGPPen.Create(aclRed, 1);

  g.Clear(aclWhite);



  for i := Low(RectArr) to High(RectArr) do

    g.DrawRectangle(p, MakeRect(RectArr[i]));



  g.Free;

  p.Free;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 179

  ClientWidth = 277

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnMouseDown = FormMouseDown

  OnMouseMove = FormMouseMove

  OnMouseUp = FormMouseUp

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

end