## 再学 GDI+[4]: DrawEllipse - 绘制椭圆 转

涂孟超

``````unit Unit1;

interface

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

type
TForm1 = class(TForm)
procedure FormPaint(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
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);
end;

var
Form1: TForm1;

implementation

{\$R *.dfm}

uses GDIPOBJ, GDIPAPI;

var
x: Integer = 20;
y: Integer = 20;
w: Integer = 100;
h: Integer = 50;
f: Byte;
a,b: Integer;
p: TGPPen;

procedure TForm1.FormCreate(Sender: TObject);
begin
p := TGPPen.Create(MakeColor(255,0,0), 2);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
p.Free;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
f := 1;
a := X;
b := Y;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
if (f = 0) then Exit;
if ssCtrl in Shift then
begin
f := 2;
Text := 'Ctrl 键被按下, 鼠标可调整大小';
end else Text := '没有按下 Ctrl 键, 鼠标可调整位置';

a := X - a;
b := Y - b;
Repaint;
a := X;
b := Y;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
f := 0;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
g: TGPGraphics;
begin
g := TGPGraphics.Create(Canvas.Handle);
g.Clear(MakeColor(255,255,255));
case f of
1: begin
Inc(x,a);
Inc(y,b);
end;
2: begin
Inc(w,a);
Inc(h,b);
end;
end;
g.DrawEllipse(p, x, y, w, h);
g.Free;
end;

end.

``````

``````object Form1: TForm1
Left = 0
Top = 0
Caption = 'Form1'
ClientHeight = 176
ClientWidth = 337
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
Position = poDesktopCenter
OnCreate = FormCreate
OnDestroy = FormDestroy
OnMouseDown = FormMouseDown
OnMouseMove = FormMouseMove
OnMouseUp = FormMouseUp
OnPaint = FormPaint
PixelsPerInch = 96
TextHeight = 13
end

``````

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