再学 GDI+[23]: TGPLinearGradientBrush - 之二

TGPLinearGradientBrush.Create(

  rect: TGPRect;                {变化范围}

  color1, color2: TGPColor;     {起始色与终止色}

  angle: Single;                {旋转角度}

  isAngleScalable: BOOL = FALSE {是否受 TLinearGradientMode 的影响, 可选值, 默认不受影响}

);



TGPLinearGradientBrush.Create(

  rect: TGPRectF;

  color1, color2: TGPColor;

  angle: Single;

  isAngleScalable: BOOL = FALSE

);


 
   

本例效果图:

---

代码文件:

---

unit Unit1;



interface



uses

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

  Dialogs, StdCtrls, TeCanvas, ExtCtrls, ComCtrls;



type

  TForm1 = class(TForm)

    ButtonColor1: TButtonColor;

    ButtonColor2: TButtonColor;

    TrackBar1: TTrackBar;

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure TrackBar1Change(Sender: TObject);

    procedure ButtonColor1Click(Sender: TObject);

    procedure ButtonColor2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI, TypInfo;



procedure TForm1.FormCreate(Sender: TObject);

begin

  ButtonColor1.Caption := '色1     ';

  ButtonColor2.Caption := '色2     ';

  ButtonColor1.SymbolColor := clLime;

  ButtonColor2.SymbolColor := clBlack;



  TrackBar1.ShowSelRange := False;

  TrackBar1.Min := 0;

  TrackBar1.Max := 360;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  lb: TGPLinearGradientBrush;

  c1,c2: TGPColor;

  r: TGPRect;

begin

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

  r := MakeRect(20, 40, ClientWidth - 40, ClientHeight - 50);

  c1 := ColorRefToARGB(ButtonColor1.SymbolColor);

  c2 := ColorRefToARGB(ButtonColor2.SymbolColor);



  lb := TGPLinearGradientBrush.Create(r, c1, c2, TrackBar1.Position);



  g.FillEllipse(lb, r);



  lb.Free;

  g.Free;

end;



procedure TForm1.TrackBar1Change(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.ButtonColor1Click(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.ButtonColor2Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 197

  ClientWidth = 253

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poScreenCenter

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object ButtonColor1: TButtonColor

    Left = 143

    Top = 8

    Width = 49

    Caption = 'ButtonColor1'

    TabOrder = 0

    OnClick = ButtonColor1Click

  end

  object ButtonColor2: TButtonColor

    Left = 198

    Top = 8

    Width = 49

    Caption = 'ButtonColor2'

    TabOrder = 1

    OnClick = ButtonColor2Click

  end

  object TrackBar1: TTrackBar

    Left = 1

    Top = 9

    Width = 137

    Height = 24

    TabOrder = 2

    OnChange = TrackBar1Change

  end

end