再学 GDI+[14]: DrawBeziers - 绘制一组贝塞尔线

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;



type

  TForm1 = class(TForm)

    procedure FormPaint(Sender: TObject);

    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);

    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

    procedure FormCreate(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ,GDIPAPI;



var

  pts: array of TGPPoint;

  ptn: Integer = -1;

  f: Boolean;



procedure TForm1.FormCreate(Sender: TObject);

begin

  Text := '按住 Ctrl 键可添加点';

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  i: Integer;

begin

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

  p := TGPPen.Create(aclRed, 1);

  g.Clear(aclWhite);



  g.DrawBeziers(p, PGPPoint(pts), Length(pts));



  p.SetColor(aclBlue);

  for i := Low(pts) to High(pts) do

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



  g.Free;

  p.Free;

end;



procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  f := True;

end;



procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

  Y: Integer);

var

  R: TRect;

  i: Integer;

begin

  if f then

  begin

    if ptn = -1 then Exit;

    pts[ptn].X := X;

    pts[ptn].Y := Y;

    Repaint;

  end else begin

    ptn := -1;

    Cursor := crDefault;

    for i := Low(pts) to High(pts) do

    begin

      R := Rect(pts[i].X-2, pts[i].Y-2, pts[i].X+2, pts[i].Y+2);

      if PtInRect(R, Point(X, Y)) then

      begin

        ptn := i;

        Cursor := crHandPoint;

      end;

    end;

  end;

end;



procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  f := False;

  if ssCtrl in Shift then

  begin

    SetLength(pts, Length(pts)+1);

    pts[High(pts)].X := X;

    pts[High(pts)].Y := Y;

    Canvas.Pen.Color := clBlue;

    Canvas.Rectangle(X-2, Y-2, X+2, Y+2);



    {当点数是 3*n+1 时再绘制}

    if Length(pts) mod 3 = 1 then Repaint;

  end;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 188

  ClientWidth = 254

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnMouseDown = FormMouseDown

  OnMouseMove = FormMouseMove

  OnMouseUp = FormMouseUp

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

end