GdiPlus[11]: IGPLinearGradientBrush 的第一种构建方式

第一种构建方式: TGPLinearGradientBrush.Create(点1, 点2, 颜色1, 颜色2);

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本例测试效果图:

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为了方便测试, 在 Unit2 单元从 TShape 继承了一个 TMyShape 类, 用来模拟一个可活动的颜色点.

其主要功能: 1、可用鼠标左键拖动; 2、可用鼠标右键改变颜色.

Unit2 的代码:

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unit Unit2;



interface



uses

  Classes, Controls, ExtCtrls, Dialogs;



type

  TMyShape = class(TShape)

  private

    fMouseFlag: Boolean;

    fx, fy: Integer;

  protected

    procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X: Integer; Y: Integer); override;

    procedure MouseUp(Button: TMouseButton; Shift: TShiftState; X: Integer; Y: Integer); override;

    procedure MouseMove(Shift: TShiftState; X: Integer; Y: Integer); override;

  public

    constructor Create(AOwner: TComponent); override;

  end;



implementation



{ TMyShape }



constructor TMyShape.Create(AOwner: TComponent);

begin

  inherited;

  Parent := TWinControl(AOwner);

  Width := 9;

  Height := 9;

  Pen.Color := $FFFFFF;

end;



procedure TMyShape.MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer);

begin

  inherited;

  if Button = mbLeft then

  begin

    fx := X;

    fy := Y;

    fMouseFlag := True;

  end;

end;



procedure TMyShape.MouseMove(Shift: TShiftState; X, Y: Integer);

begin

  inherited;

  if fMouseFlag then

  begin

    Left := Left + X - fx;

    Top := Top + Y - fy;

    TWinControl(Owner).Repaint;

  end;

end;



procedure TMyShape.MouseUp(Button: TMouseButton; Shift: TShiftState; X, Y: Integer);

begin

  inherited;

  fMouseFlag := False;

  if Button = mbRight then

  begin

    with TColorDialog.Create(Owner) do if Execute then Brush.Color := Color;

  end;

  TWinControl(Owner).Repaint;

end;



end.


 
   

Unit1 代码:

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unit Unit1;



interface



uses

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

  Dialogs;



type

  TForm1 = class(TForm)

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GdiPlus, GdiPlusHelpers, Unit2;



var

  Shape1, Shape2: TMyShape;



procedure TForm1.FormCreate(Sender: TObject);

begin

  Shape1 := TMyShape.Create(Self);

  Shape1.Left := 10;

  Shape1.Top := 10;

  shape1.Brush.Color := clRed;



  Shape2 := TMyShape.Create(Self);

  Shape2.Left := ClientWidth - 10 - Shape2.Width;

  Shape2.Top := ClientHeight - 10 - Shape2.Height;

  Shape2.Brush.Color := clBlue;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  Brush: IGPLinearGradientBrush;

  Pt1,Pt2: TGPPoint;

  Color1, Color2: TGPColor;

  Rect: TRect;

begin

  Pt1.Initialize(Shape1.Left + Shape1.Width div 2, Shape1.Top + Shape1.Height div 2);

  Pt2.Initialize(Shape2.Left + Shape2.Width div 2, Shape2.Top + Shape2.Height div 2);

  Color1 := TGPColor.CreateFromColorRef(Shape1.Brush.Color);

  Color2 := TGPColor.CreateFromColorRef(Shape2.Brush.Color);



  Brush := TGPLinearGradientBrush.Create(Pt1, Pt2, Color1, Color2);



  Rect := ClientRect;

  InflateRect(Rect, -ClientWidth div 10, -ClientHeight div 10);

  Canvas.ToGPGraphics.FillEllipse(Brush, TGPRect.Create(Rect));

end;



end.