再学GDI+[37]

TGPPen - TGPCustomLineCap、SetCustomStartCap、SetCustomEndCap

GDI+ 可以自定义线帽, 本例定义的起始线帽是一个小矩形、终止线帽是一个小三角形.

本例效果图:

代码文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, ExtCtrls;
type
　TForm1 = class(TForm)
　　procedure FormCreate(Sender: TObject);
　　procedure FormDestroy(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);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
var
　ph1,ph2: TGPGraphicsPath;
　cap1,cap2: TGPCustomLineCap;
　x1,y1,x2,y2: Integer;
　f: Boolean;
　PenColor: TColor;
procedure TForm1.FormCreate(Sender: TObject);
const
　pts: array[0..2] of TGPPoint = ((X:-3; Y:0),(X:3; Y:0),(X:0; Y:3));
begin
　{起始线帽需要的路径}
　ph1 := TGPGraphicsPath.Create;
　ph1.AddRectangle(MakeRect(-2, 0, 4, 3));
　{终止线帽需要的路径}
　ph2 := TGPGraphicsPath.Create;
　ph2.AddPolygon(PGPPoint(@pts), Length(pts));
　{自定义两个线帽}
　cap1 := TGPCustomLineCap.Create(nil, ph1);
　cap2 := TGPCustomLineCap.Create(nil, ph2);
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
　ph1.Free;
　ph2.Free;
　cap1.Free;
　cap2.Free;
end;
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　f := True;
　x1 := X;
　y1 := Y;
　x2 := X;
　y2 := Y;
　Randomize;
　PenColor := Random($FFFFFF);　　　　　　　{给画笔一个随机颜色}
　Canvas.Pen.Color := $FFFFFF xor PenColor; {取画笔反色, 为了在 pmXor 模式下显示真 实的颜色}
　Canvas.Pen.Width := 3;
　Canvas.Pen.Mode := pmXor;
end;
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
　Y: Integer);
begin
　if not f then Exit;
　Canvas.MoveTo(x1, y1);
　Canvas.LineTo(x2,y2);
　x2 := X;
　y2 := Y;
　Canvas.MoveTo(x1, y1);
　Canvas.LineTo(x2,y2);
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
var
　g: TGPGraphics;
　p: TGPPen;
begin
　if not f then Exit;
　f := False;
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(ColorRefToARGB(PenColor), 3);
　{使用自定义线帽}
　p.SetCustomStartCap(cap1);
　p.SetCustomEndCap(cap2);
　g.DrawLine(p, x1, y1, x2, y2);
　p.Free;
　g.Free;
end;
end.

窗体文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClientHeight = 193
　ClientWidth = 296
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnCreate = FormCreate
　OnDestroy = FormDestroy
　OnMouseDown = FormMouseDown
　OnMouseMove = FormMouseMove
　OnMouseUp = FormMouseUp
　PixelsPerInch = 96
　TextHeight = 13
end