再学 GDI+[25]: TGPPen - 宽度、颜色与线帽

本例效果图:

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代码文件:

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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.

窗体文件:

---

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

附线帽样式常数:

---

LineCapFlat          = 0;   {指定平线帽}
LineCapSquare        = 1;   {指定方线帽}
LineCapRound         = 2;   {指定圆线帽}
LineCapTriangle      = 3;   {指定三角线帽}
LineCapNoAnchor      = $10; {指定没有锚}
LineCapSquareAnchor  = $11; {指定方锚头帽}
LineCapRoundAnchor   = $12; {指定圆锚头帽}
LineCapDiamondAnchor = $13; {指定菱形锚头帽}
LineCapArrowAnchor   = $14; {指定箭头状锚头帽}
LineCapCustom        = $ff; {指定自定义线帽}

LineCapAnchorMask    = $f0; {定用于检查线帽是否为锚头帽的掩码}