再学 GDI+[55]: 路径 Flatten

通过路径的 Flatten 方法可以把路径中的曲线拉直, 拉直到什么程度是由它的第二个参数(默认0.25)决定的; 它的第一个参数又是一个矩阵变换, 也就是说 Flatten 可以同时进行矩阵变换, 本例没有测试它, 其详情参见:
http://www.cnblogs.com/del/archive/2008/06/20/1226293.html

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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, ComCtrls;

type
  TForm1 = class(TForm)
    TrackBar1: TTrackBar;
    procedure FormPaint(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormCreate(Sender: TObject);
begin
  TrackBar1.Height := 23;
  TrackBar1.ShowSelRange := False;
  TrackBar1.Min := -5000;
  TrackBar1.Max := 5000;
  TrackBar1.Position := 25;
  TrackBar1.PageSize := 5;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
  path: TGPGraphicsPath;
  f: Single;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclBlue, 2);
  path := TGPGraphicsPath.Create;
  path.AddEllipse(20, 20, ClientWidth-40, ClientHeight- 80);

  f := TrackBar1.Position / 100;
  path.Flatten(nil, f);
  Text := Format('%f', [f]);

  g.DrawPath(p, path);

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

procedure TForm1.TrackBar1Change(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 200
  ClientWidth = 264
  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 TrackBar1: TTrackBar
    Left = 0
    Top = 176
    Width = 265
    Height = 45
    TabOrder = 0
    OnChange = TrackBar1Change
  end
end