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