再学 GDI+[62]: 路径画刷(2) SetCenterPoint、GetCenterPoint

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, CheckLst, ExtCtrls, TeCanvas;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

var
  rect: TGPRect;
  pt: TGPPoint;
  pb: TGPPathGradientBrush;

procedure TForm1.FormCreate(Sender: TObject);
var
  path: TGPGraphicsPath;
  ColorSurround: TGPColor;  {只用一种包围色, 就别用数组了}
  num: Integer;
begin
  rect := MakeRect(10, 10, ClientWidth-20, ClientHeight-20);
  path := TGPGraphicsPath.Create;
  path.AddEllipse(rect);

  pb := TGPPathGradientBrush.Create(path);
  pb.SetCenterColor(aclLime);

  pb.GetCenterPoint(pt);

  ColorSurround := aclBlack;
  num := 1;
  pb.SetSurroundColors(@ColorSurround, num);

  path.Free;

  DoubleBuffered := True;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  pb.Free;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  pt.X := X;
  pt.Y := Y;
  Repaint;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Repaint;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclRed);

  g.FillEllipse(pb, rect);
  pb.SetCenterPoint(pt);
  g.DrawRectangle(p, pt.X-3, pt.Y-3, 6, 6);

  p.Free;
  g.Free;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 164
  ClientWidth = 208
  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
  OnMouseUp = FormMouseUp
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
end