再学 GDI+[52]: 路径 Reverse、Reset

本例效果图:

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代码文件:

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unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    CheckBox1: TCheckBox;
    CheckBox2: TCheckBox;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure CheckBox1Click(Sender: TObject);
    procedure CheckBox2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

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

procedure TForm1.FormCreate(Sender: TObject);
begin
  pts[0].X := 10;  pts[0].Y := 50;
  pts[1].X := 40;  pts[1].Y := 90;
  pts[2].X := 80;  pts[2].Y := 10;
  pts[3].X := 110;  pts[3].Y := 50;
  pts[4].X := 140;  pts[4].Y := 10;
  pts[5].X := 180; pts[5].Y := 90;
  pts[6].X := 210; pts[6].Y := 50;

  CheckBox1.Caption := '翻转路径中的点';
  CheckBox2.Caption := '清空路径中的点';
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
  path: TGPGraphicsPath;
  PathPts: array of TGPPoint;
  i: Integer;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclRed, 2);
  path := TGPGraphicsPath.Create;
  path.AddBeziers(PGPPoint(@pts), Length(pts));

  if CheckBox1.Checked then path.Reverse;
  if CheckBox2.Checked then path.Reset;
  {Reset 时, 会清空 PathPoints 和 PathTypes 数组并将 FillMode 设置为 FillModeAlternate}

  SetLength(PathPts, path.GetPointCount);
  path.GetPathPoints(PGPPoint(PathPts), Length(PathPts));

  Canvas.Pen.Color := clGray;
  for i := Low(PathPts) to High(PathPts) do
    Canvas.TextOut(PathPts[i].X, PathPts[i].Y, IntToStr(i+1));

  g.DrawPath(p, path);

  path.Free;
  p.Free;
  g.Free;
end;

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  Repaint;
end;

procedure TForm1.CheckBox2Click(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 156
  ClientWidth = 232
  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 = 12
    Top = 126
    Width = 113
    Height = 17
    Caption = 'CheckBox1'
    TabOrder = 0
    OnClick = CheckBox1Click
  end
  object CheckBox2: TCheckBox
    Left = 123
    Top = 126
    Width = 106
    Height = 17
    Caption = 'CheckBox2'
    TabOrder = 1
    OnClick = CheckBox2Click
  end
end