再學GDI+[25]: TGPPen - 寬度、顏色與線帽

本例效果圖:

代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, TeCanvas, ComCtrls;
type
　TForm1 = class(TForm)
　　ComboBox1: TComboBox;
　　ComboBox2: TComboBox;
　　TrackBar1: TTrackBar;
　　ButtonColor1: TButtonColor;
　　procedure FormCreate(Sender: TObject);
　　procedure FormPaint(Sender: TObject);
　　procedure ComboBox1Change(Sender: TObject);
　　procedure ComboBox2Change(Sender: TObject);
　　procedure TrackBar1Change(Sender: TObject);
　　procedure ButtonColor1Click(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ,GDIPAPI, TypInfo;
var
　StartCap, EndCap: Integer;
　LineWidth: Single = 2;
　LineColor: TGPColor = aclRed;
procedure TForm1.FormCreate(Sender: TObject);
begin
　with ComboBox1.Items do
　begin
　　Add('LineCapFlat');
　　Add('LineCapSquare');
　　Add('LineCapRound');
　　Add('LineCapTriangle');
　　Add('LineCapNoAnchor');
　　Add('LineCapSquareAnchor');
　　Add('LineCapRoundAnchor');
　　Add('LineCapDiamondAnchor');
　　Add('LineCapArrowAnchor');
　　Add('LineCapCustom');
　end;
　ComboBox1.ItemIndex := 0;
　ComboBox2.Items := ComboBox1.Items;
　ComboBox2.ItemIndex := 0;
　TrackBar1.ShowSelRange := False;
　TrackBar1.Min := 1;
　TrackBar1.Max := 50;
　TrackBar1.Position := 2;
　ButtonColor1.SymbolColor := clRed;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
　x1,y1,x2,y2: Integer;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(0);
　g.Clear(MakeColor(255,255,255));
　x1 := 50;
　x2 := ClientWidth - 50;
　y1 := ClientHeight div 2;
　y2 := y1;
　p.SetColor(LineColor);
　p.SetWidth(LineWidth);
　p.SetStartCap(StartCap);
　p.SetEndCap(EndCap);
　g.DrawLine(p, x1, y1, x2, y2);
　g.Free;
　p.Free;
end;
procedure TForm1.ComboBox1Change(Sender: TObject);
var
　i: Integer;
begin
　i := 0;
　case TComboBox(Sender).ItemIndex of
　　0 : i := LineCapFlat;
　　1 : i := LineCapSquare;
　　2 : i := LineCapRound;
　　3 : i := LineCapTriangle;
　　4 : i := LineCapNoAnchor;
　　5 : i := LineCapSquareAnchor;
　　6 : i := LineCapRoundAnchor;
　　7 : i := LineCapDiamondAnchor;
　　8 : i := LineCapArrowAnchor;
　　9 : i := LineCapCustom;
　　10: i := LineCapAnchorMask;
　end;
　if TComboBox(Sender) = ComboBox1 then StartCap := i;
　if TComboBox(Sender) = ComboBox2 then EndCap := i;
　Repaint;
end;
procedure TForm1.ComboBox2Change(Sender: TObject);
begin
　ComboBox1Change(Sender);
end;
procedure TForm1.TrackBar1Change(Sender: TObject);
begin
　LineWidth := TrackBar1.Position;
　Repaint;
end;
procedure TForm1.ButtonColor1Click(Sender: TObject);
begin
　LineColor := ColorRefToARGB(ButtonColor1.SymbolColor);
　Repaint;
end;
end.

窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClientHeight = 206
　ClientWidth = 315
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnCreate = FormCreate
　OnPaint = FormPaint
　PixelsPerInch = 96
　TextHeight = 13
　object ComboBox1: TComboBox
　　Left = 8
　　Top = 8
　　Width = 145
　　Height = 21
　　ItemHeight = 13
　　TabOrder = 0
　　Text = 'ComboBox1'
　　OnChange = ComboBox1Change
　end
　object ComboBox2: TComboBox
　　Left = 162
　　Top = 8
　　Width = 145
　　Height = 21
　　ItemHeight = 13
　　TabOrder = 1
　　Text = 'ComboBox2'
　　OnChange = ComboBox2Change
　end
　object TrackBar1: TTrackBar
　　Left = 3
　　Top = 182
　　Width = 223
　　Height = 20
　　TabOrder = 2
　　OnChange = TrackBar1Change
　end
　object ButtonColor1: TButtonColor
　　Left = 232
　　Top = 177
　　Caption = 'ButtonColor1'
　　TabOrder = 3
　　OnClick = ButtonColor1Click
　end
end

附線帽樣式常數:LineCapFlat= 0;　 {指定平線帽}
LineCapSquare　　　　= 1;　 {指定方線帽}
LineCapRound　　　　 = 2;　 {指定圓線帽}
LineCapTriangle　　　= 3;　 {指定三角線帽}
LineCapNoAnchor　　　= $10; {指定沒有錨}
LineCapSquareAnchor　= $11; {指定方錨頭帽}
LineCapRoundAnchor　 = $12; {指定圓錨頭帽}
LineCapDiamondAnchor = $13; {指定菱形錨頭帽}
LineCapArrowAnchor　 = $14; {指定箭頭狀錨頭帽}
LineCapCustom　　　　= $ff; {指定自定義線帽}
LineCapAnchorMask　　= $f0; {定用於檢查線帽是否為錨頭帽的掩碼}