再学 GDI+[14]: DrawBeziers - 绘制一组贝塞尔线

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);
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.

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