如何在 GDI+ 中指定旋转中心 - 回复 "wuheng66888" 的问题

问题来源: http://www.cnblogs.com/del/archive/2009/01/23/1017571.html#1437673

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本来 wuheng66888 需要的是输出旋转的文本, 下面的例子只是转了一个矩形;
因为 GDI+ 的旋转理念是旋转画布, 所以都是一样的.

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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;



type

  TForm1 = class(TForm)

    procedure FormPaint(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  rect: TGPRect;

  pt: TGPPointF;

  Matrix: TGPMatrix;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  p := TGPPen.Create(MakeColor(255,255,0,0),0);



  rect := MakeRect(30,30,100,100);



  {譬如准备在上面矩形的中心点旋转}

  pt := MakePoint(rect.X + rect.Width / 2, rect.Y + rect.Height /2);



  Matrix := TGPMatrix.Create;

  Matrix.RotateAt(45, pt); {以指定的 pt 为中心, 转 45° 角}



  {先画个不旋转的}

  g.DrawRectangle(p, rect);



  {再画个旋转的}

  p.SetColor(aclBlue);

  g.SetTransform(Matrix);  {关键代码}

  g.DrawRectangle(p, rect);



  g.ResetTransform;        {关键代码, 不恢复后面就都旋转了}



  Matrix.Free;

  p.Free;

  g.Free;

end;



end.