Delphi绘图功能[2] —— 窗体的绘图属性、圆弧类图形、获取Canvas对象(ClientRect解析)

CopyRect(const Dest:TRect;Canvas:TCanvas;const Source:TRect);
{参数Dest表示目的矩形区域，Canvas表示原画布，Source表示原矩形区域}

Draw(X,Y:Integer，Graphic：TGraphic);
{说明：X，Y表示绘制位置的x，y坐标，Graphic表示要画到画布上的位图，图标或图源文件}

unit Unit1;
interface
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls, Vcl.ComCtrls;
type
  TForm1 = class(TForm)
    {PageControl1: TPageControl;
    TabSheet1: TTabSheet;
    TabSheet2: TTabSheet;
    TabSheet3: TTabSheet;
    TabSheet4: TTabSheet;}
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.dfm}
var
  btn : TButton;
//如果参数在函数中不可能修改, 一定要使用 const
const            //这里设置了不可修改的两个值
  y1 = 100;
  y2 = 500;
{2、根据矩形结构绘制椭圆}
procedure TForm1.Button2Click(Sender: TObject);
var
  R:TRect;  //定义一个矩形结构
begin
  btn:=TButton(Sender);
  R:= Rect(btn.Left,y1,btn.Left+btn.Width,y2);
  Canvas.Ellipse(R);
end;
{3、绘制扇形}
procedure TForm1.Button3Click(Sender: TObject);
begin
  btn := TButton(Sender);
  Canvas.Pie(
    btn.Left, y1,                             {矩形区域左上角}
    btn.Left + btn.Width, y2,                 {矩形区域右下角}
    btn.Left + btn.Width, y1 + (y2-y1) div 2, {扇形起点}
    btn.Left + btn.Width div 2, y1            {扇形终点}
  );
end;
{4、绘制弦，参数和扇形一样}
procedure TForm1.Button4Click(Sender: TObject);
begin
  btn := TButton(Sender);
  Canvas.Chord(
    btn.Left, y1,
    btn.Left + btn.Width, y2,
    btn.Left + btn.Width, y1 + (y2-y1) div 2,
    btn.Left + btn.Width div 2, y1
  );
end;
{5、绘制弧线}
procedure TForm1.Button5Click(Sender: TObject);
begin
  btn := TButton(Sender);
  Canvas.Arc(
    btn.Left, y1,
    btn.Left + btn.Width, y2,
    btn.Left + btn.Width, y1 + (y2-y1) div 2,
    btn.Left + btn.Width div 2, y1
  );
end;
{在form打开时就自动创建画笔画刷}
procedure TForm1.FormCreate(Sender: TObject);
begin
  Canvas.Pen.Width := 4;
  Canvas.Pen.Color := clRed;
  Canvas.Brush.Color := clWhite;   //设置画刷颜色
end;
{1、绘制椭圆; 椭圆的参数和矩形是一样的}
procedure TForm1.Button1Click(Sender: TObject);
begin
   btn:= TButton(sender);
   Canvas.Ellipse(btn.left,y1,btn.left+btn.width,y2);
end;
end.