再学 GDI+[13]: DrawBezier - 绘制贝塞尔线

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);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ,GDIPAPI;

var
pts: array[0..3] of TGPPoint = ((X:30;Y:100),(X:120;Y:10),(X:170;Y:150),(X:220;Y:100));
ptn: Integer = -1;
f: Boolean;

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.DrawBezier(p, pts[0], pts[1], pts[2], pts[3]);

p.SetColor(aclBlue);
for i := 0 to 3 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;
for i := 0 to 3 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 ptn := i;
end;
end;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
f := False;
end;

end.

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
OnMouseDown = FormMouseDown
OnMouseMove = FormMouseMove
OnMouseUp = FormMouseUp
OnPaint = FormPaint
PixelsPerInch = 96
TextHeight = 13
end