WinAPI: FlattenPath、WidenPath

不管什么曲线命令, 到来路径中都会变成 Bezier 线; 也就是说路径中只有直线和 Bezier 线.

FlattenPath 和 WidenPath 都能够把路径中的 Bezier 线转换为近似的直线; 不同的是: 用 WidenPath 转换后貌似加宽了线, 其实它是转换成了一个包围路径的新路径(类似区域).

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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, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    RadioGroup1: TRadioGroup;

    procedure FormPaint(Sender: TObject);

    procedure FormCreate(Sender: TObject);

    procedure RadioGroup1Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);

begin

  RadioGroup1.Items.CommaText := 'Path,FlattenPath,WidenPath';

  RadioGroup1.ItemIndex := 0;

end;



procedure TForm1.FormPaint(Sender: TObject);

type

  TPArr = array[0..0] of TPoint;

  TTArr = array[0..0] of Byte;

var

  pts: ^TPArr;

  types: ^TTArr;

  count: Integer;

  i,x,y: Integer;

begin

  Canvas.Font.Size := 150;

  Canvas.Font.Style := [fsBold];

  SetBkMode(Canvas.Handle, TRANSPARENT);



  BeginPath(Canvas.Handle);

  Canvas.TextOut(50, 0, 'D');

  Canvas.Arc(20, 20, 220, 220, 120, 120, 20, 120);

  EndPath(Canvas.Handle);



  Canvas.Pen.Width := 6;



  if RadioGroup1.ItemIndex = 1 then FlattenPath(Canvas.Handle);

  if RadioGroup1.ItemIndex = 2 then WidenPath(Canvas.Handle);



  Canvas.Pen.Color := clWhite;

  count := GetPath(Canvas.Handle, pts^, types^, 0);



  GetMem(pts, count*SizeOf(TPoint));

  GetMem(types, count);



  count := GetPath(Canvas.Handle, pts^, types^, count);

  Text := '路径中点的总数是: ' + IntToStr(count);



  StrokePath(Canvas.Handle);



  Canvas.Brush.Color := clRed;

  for i := 0 to count - 1 do

  begin

    x := pts^[i].X;

    y := pts^[i].Y;

    Canvas.FillRect(Rect(x-1,y-1,x+1,y+1));

  end;



  FreeMem(pts);

  FreeMem(types);

end;



procedure TForm1.RadioGroup1Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 352

  Top = 227

  Caption = 'Form1'

  ClientHeight = 215

  ClientWidth = 339

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesigned

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object RadioGroup1: TRadioGroup

    Left = 240

    Top = 80

    Width = 91

    Height = 127

    Caption = 'RadioGroup1'

    TabOrder = 0

    OnClick = RadioGroup1Click

  end

end


 
   

关于描绘路径中的点, 参见: http://www.cnblogs.com/del/archive/2008/05/26/1207423.html

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