再学 GDI+[49]: 路径 - GetPointCount、GetPathPoints、GetLastPoint、GetBounds

本例效果图:

---

代码文件:

---

unit Unit1;



interface



uses

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

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    CheckBox1: TCheckBox;

    CheckBox2: TCheckBox;

    CheckBox3: TCheckBox;

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure CheckBox1Click(Sender: TObject);

    procedure CheckBox2Click(Sender: TObject);

    procedure CheckBox3Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



procedure TForm1.FormCreate(Sender: TObject);

begin

  CheckBox1.Caption := '提取路径中所有的点';

  CheckBox2.Caption := '提取路径中最后一个点';

  CheckBox3.Caption := '显示路径的外接矩形';

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  path: TGPGraphicsPath;

  p: TGPPen;

  b: TGPBrush;

  pts: array[0..6] of TGPPoint;

  ptf: TGPPointF;

  ppts: array of TGPPoint;

  rect: TGPRect;

  i: Integer;

begin

  {给 Bezier 线准备的点, 用于建立路径}

  pts[0].X := 22;  pts[0].Y := 44;

  pts[1].X := 11;  pts[1].Y := 111;

  pts[2].X := 33;  pts[2].Y := 222;

  pts[3].X := 60;  pts[3].Y := 88;

  pts[4].X := 80;  pts[4].Y := 222;

  pts[5].X := 170; pts[5].Y := 111;

  pts[6].X := 200; pts[6].Y := 11;



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



  {建立路径, 并给路径添加两条 Bezier 线}

  path := TGPGraphicsPath.Create;

  path.AddBeziers(PGPPoint(@pts), Length(pts));



  {绘制路径}

  p := TGPPen.Create(aclRed);

  g.DrawPath(p, path);



  {虚画原始数据点}

  p.SetColor(aclGray);

  for i := 0 to Length(pts)-1 do

    g.DrawRectangle(p, MakeRect(pts[i].X-2, pts[i].Y-2, 4, 4));



  {提取路径中所有的点}

  b := TGPSolidBrush.Create(aclBlue);

  if CheckBox1.Checked then

  begin

    SetLength(ppts, path.GetPointCount);

    path.GetPathPoints(PGPPoint(ppts), Length(pts));

    for i := 0 to Length(ppts)-1 do

      g.FillRectangle(b, MakeRect(ppts[i].X-3, ppts[i].Y-3, 6, 6));

  end;



  {可以专门获取最后一个点}

  TGPSolidBrush(b).SetColor(aclRed);

  if CheckBox2.Checked then

  begin

    path.GetLastPoint(ptf);

    g.FillRectangle(b, MakeRect(ptf.X-3, ptf.Y-3, 6, 6));

  end;



  {路径的外接矩形}

  if CheckBox3.Checked then

  begin

    path.GetBounds(rect);

    g.DrawRectangle(p, rect);

  end;



  b.Free;

  p.Free;

  path.Free;

  g.Free;

end;



procedure TForm1.CheckBox1Click(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.CheckBox2Click(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.CheckBox3Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 235

  ClientWidth = 302

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object CheckBox1: TCheckBox

    Left = 157

    Top = 152

    Width = 124

    Height = 17

    Caption = 'CheckBox1'

    TabOrder = 0

    OnClick = CheckBox1Click

  end

  object CheckBox2: TCheckBox

    Left = 157

    Top = 175

    Width = 137

    Height = 17

    Caption = 'CheckBox2'

    TabOrder = 1

    OnClick = CheckBox2Click

  end

  object CheckBox3: TCheckBox

    Left = 157

    Top = 198

    Width = 137

    Height = 17

    Caption = 'CheckBox3'

    TabOrder = 2

    OnClick = CheckBox3Click

  end

end