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  • 再学 GDI+[4]: DrawEllipse 绘制椭圆

    本例效果图:



    代码文件:
    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.
    
    窗体文件:
    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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  • 原文地址:https://www.cnblogs.com/del/p/1215936.html
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