GdiPlus[3]: 关于 GdiPlusHelpers 单元

本套接口只有两个单元: GdiPlus, GdiPlusHelpers; 主要的是前者, GdiPlusHelpers 的作用是通过 Helper 技术给 VCL 体系中的 TCanvas、TGraphicControl、TCustomControl、TBitmap 类补充添加 ToGPGraphics 方法, 以方便获取 IGPGraphics.

在很多时候我们并不需要它, 这时也不需要 uses GdiPlusHelpers.

不过这对有些对象会很方便, 譬如: uses GdiPlusHelpers 后, TPanel 也有了 ToGPGraphics 方法.

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尝试下面代码前, 先在窗体上添加 TImage、TPaintBox、TPanel 对象各一个.

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本例效果图:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, ExtCtrls;



type

  TForm1 = class(TForm)

    Panel1: TPanel;

    Image1: TImage;

    PaintBox1: TPaintBox;

    procedure FormPaint(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GdiPlus, GdiPlusHelpers;



procedure TForm1.FormPaint(Sender: TObject);

var

  Pen: IGPPen;

begin

  Pen := TGPPen.Create(TGPColor.Red);

  Image1.ToGPGraphics.DrawLine(Pen, 0, 0, Image1.Width, Image1.Height);

  Image1.ToGPGraphics.DrawLine(Pen, 0, Image1.Height, Image1.Width, 0);



  Pen.Color := TGPColor.LimeGreen;

  PaintBox1.ToGPGraphics.DrawLine(Pen, 0, 0, PaintBox1.Width, PaintBox1.Height);

  PaintBox1.ToGPGraphics.DrawLine(Pen, 0, PaintBox1.Height, PaintBox1.Width, 0);



  Pen.Color := TGPColor.Blue;

  Panel1.ToGPGraphics.DrawLine(Pen, 0, 0, Panel1.ClientWidth, Panel1.Height);

  Panel1.ToGPGraphics.DrawLine(Pen, 0, Panel1.Height, Panel1.ClientWidth, 0);

end;



end.