再学 GDI+[31]: TGPPen - 设置端点连接方式

本文介绍了一种使用 Delphi 实现不同端点连接样式的图形绘制方法。通过枚举 TLineJoin 类型的不同选项，文章展示了如何在窗体上绘制具有不同连接样式的多边形。此外，还提供了一个响应 ListBox 选择更改来更新显示效果的示例。

本例效果图:

代码文件:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure ListBox1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI, TypInfo;

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  for i := 0 to 3 do
    ListBox1.Items.Add(GetEnumName(TypeInfo(TLineJoin),i));
  ListBox1.ItemIndex := 0;
end;

procedure TForm1.FormPaint(Sender: TObject);
const
  PtArr: array[0..2] of TGPPoint = ((X:50;Y:150), (X:240;Y:30), (X:240;Y:150));
var
  g: TGPGraphics;
  p: TGPPen;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclBlueViolet, 28);
  p.SetLineJoin(TLineJoin(ListBox1.ItemIndex));

  g.DrawPolygon(p, PGPPoint(@PtArr), Length(PtArr));

  p.Free;
  g.Free;
end;

procedure TForm1.ListBox1Click(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 177
  ClientWidth = 382
  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 ListBox1: TListBox
    Left = 277
    Top = 0
    Width = 105
    Height = 177
    Align = alRight
    ItemHeight = 13
    TabOrder = 0
    OnClick = ListBox1Click
    ExplicitHeight = 173
  end
end

端点连接方式枚举:

LineJoin = (
  LineJoinMiter,
  LineJoinBevel,
  LineJoinRound,
  LineJoinMiterClipped
);
TLineJoin = LineJoin;

再学 GDI+[31]: TGPPen - 设置端点连接方式 - SetLineJoin