unit Unit1;interfaceusesWindows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs, StdCtrls, ComCtrls, ExtCtrls;typeTForm1 = class(TForm)Button1: TButton;TrackBar1: TTrackBar;LabeledEdit1: TLabeledEdit;LabeledEdit2: TLabeledEdit;procedure FormMouseUp(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);procedure FormPaint(Sender: TObject);procedure FormCreate(Sender: TObject);procedure Button1Click(Sender: TObject);procedure TrackBar1Change(Sender: TObject);procedure LabeledEdit1Change(Sender: TObject);procedure LabeledEdit2Change(Sender: TObject);end;varForm1: TForm1;implementation{$R *.dfm}uses GDIPOBJ, GDIPAPI;varPtArr: array of TGPPoint;i: Integer = 0;tension: Single;procedure TForm1.FormCreate(Sender: TObject);
beginButton1.Caption := '擦除';LabeledEdit1.EditLabel.Caption := '起始点';LabeledEdit2.EditLabel.Caption := '有效点数';LabeledEdit1.Text := '0';LabeledEdit2.Text := '0';TrackBar1.ShowSelRange := False;TrackBar1.Min := -25;TrackBar1.Max := 35;TrackBar1.Position := 5;
end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
beginInc(i);SetLength(PtArr, i);PtArr[i-1].X := X;PtArr[i-1].Y := Y;LabeledEdit2.Text := IntToStr(i-1);Text := IntToStr(i);Repaint;
end;procedure TForm1.FormPaint(Sender: TObject);
varg: TGPGraphics;p: TGPPen;i,n1,n2: Integer;
beging := TGPGraphics.Create(Canvas.Handle);p := TGPPen.Create(aclRed, 2);g.Clear(aclWhite);n1 := StrToIntDef(LabeledEdit1.Text, 0);n2 := StrToIntDef(LabeledEdit2.Text, Length(PtArr)-1);{后面三个参数是可选的, 最后参数的默认值是 0.5, 为 0 时曲线会转为直线段}g.DrawCurve(p, PGPPoint(PtArr), Length(PtArr), n1, n2, tension);p.SetWidth(1);p.SetColor(aclBlack);for i := 0 to Length(PtArr) - 1 dog.DrawEllipse(p, PtArr[i].X-2, PtArr[i].Y-2, 4, 4);g.Free;p.Free;
end;procedure TForm1.LabeledEdit1Change(Sender: TObject);
vara,b: Integer;
begina := StrToIntDef(LabeledEdit1.Text, 0);if (a < 0) or (a > Length(PtArr) - 2) thenLabeledEdit1.Text := IntToStr(0);a := StrToIntDef(LabeledEdit1.Text, 0);b := StrToIntDef(LabeledEdit2.Text, 0);if a+b > Length(PtArr)-1 thenLabeledEdit2.Text := IntToStr(Length(PtArr)-1-a);Repaint;
end;procedure TForm1.LabeledEdit2Change(Sender: TObject);
vara,b: Integer;
begina := StrToIntDef(LabeledEdit1.Text, 0);b := StrToIntDef(LabeledEdit2.Text, 0);if (b < 0) or (b >= Length(PtArr) - a) thenLabeledEdit2.Text := IntToStr(Length(PtArr)-1-a);Repaint;
end;procedure TForm1.TrackBar1Change(Sender: TObject);
begintension := TrackBar1.Position / 10;Repaint;
end;procedure TForm1.Button1Click(Sender: TObject);
begini := 0;SetLength(PtArr, i);Repaint;Text := IntToStr(i);
end;end.

窗体文件:

object Form1: TForm1Left = 0Top = 0Caption = 'Form1'ClientHeight = 187ClientWidth = 264Color = clBtnFaceFont.Charset = DEFAULT_CHARSETFont.Color = clWindowTextFont.Height = -11Font.Name = 'Tahoma'Font.Style = []OldCreateOrder = FalsePosition = poDesktopCenterOnCreate = FormCreateOnMouseUp = FormMouseUpOnPaint = FormPaintPixelsPerInch = 96TextHeight = 13object Button1: TButtonLeft = 181Top = 155Width = 75Height = 25Caption = 'Button1'TabOrder = 0OnClick = Button1Clickendobject TrackBar1: TTrackBarLeft = 8Top = 155Width = 167Height = 25TabOrder = 1OnChange = TrackBar1Changeendobject LabeledEdit1: TLabeledEditLeft = 208Top = 54Width = 48Height = 21EditLabel.Width = 61EditLabel.Height = 13EditLabel.Caption = 'LabeledEdit1'TabOrder = 2OnChange = LabeledEdit1Changeendobject LabeledEdit2: TLabeledEditLeft = 208Top = 102Width = 48Height = 21EditLabel.Width = 61EditLabel.Height = 13EditLabel.Caption = 'LabeledEdit2'TabOrder = 3OnChange = LabeledEdit2Changeend
end