再学 GDI+[22]: TGPLinearGradientBrush - 之一: TLinearGradientMode

TGPLinearGradientBrush.Create(

  rect: TGPRect;            {线性渐变的界限}

  color1, color2: TGPColor; {线性渐变起始色与终止色}

  mode: TLinearGradientMode {渐变方向, 见下表}

);



TGPLinearGradientBrush.Create(

  rect: TGPRectF;

  color1, color2: TGPColor;

  mode: TLinearGradientMode

);


 
   

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, TeCanvas;



type

  TForm1 = class(TForm)

    ComboBox1: TComboBox;

    ButtonColor1: TButtonColor;

    ButtonColor2: TButtonColor;

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure ButtonColor1Click(Sender: TObject);

    procedure ButtonColor2Click(Sender: TObject);

    procedure ComboBox1Change(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI, TypInfo;



procedure TForm1.FormCreate(Sender: TObject);

var

  i: Integer;

begin

  for i := 0 to 3 do

    ComboBox1.Items.Add(GetEnumName(TypeInfo(TLinearGradientMode), i));

  ComboBox1.ItemIndex := 1;



  ButtonColor1.Caption := '色1     ';

  ButtonColor2.Caption := '色2     ';

  ButtonColor1.SymbolColor := clYellow;

  ButtonColor2.SymbolColor := clRed;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  lb: TGPLinearGradientBrush;

  c1,c2: TGPColor;

  r: TGPRect;

begin

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

  r := MakeRect(60, 40, ClientWidth - 120, ClientHeight - 50);

  c1 := ColorRefToARGB(ButtonColor1.SymbolColor);

  c2 := ColorRefToARGB(ButtonColor2.SymbolColor);

  lb := TGPLinearGradientBrush.Create(r, c1, c2, TLinearGradientMode(ComboBox1.ItemIndex));



  g.FillEllipse(lb, r);



  lb.Free;

  g.Free;

end;



procedure TForm1.ButtonColor1Click(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.ButtonColor2Click(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.ComboBox1Change(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 197

  ClientWidth = 309

  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 ComboBox1: TComboBox

    Left = 113

    Top = 6

    Width = 192

    Height = 21

    ItemHeight = 13

    TabOrder = 0

    Text = 'ComboBox1'

    OnChange = ComboBox1Change

  end

  object ButtonColor1: TButtonColor

    Left = 5

    Top = 4

    Width = 49

    Caption = 'ButtonColor1'

    TabOrder = 1

    OnClick = ButtonColor1Click

  end

  object ButtonColor2: TButtonColor

    Left = 58

    Top = 4

    Width = 49

    Caption = 'ButtonColor2'

    TabOrder = 2

    OnClick = ButtonColor2Click

  end

end


 
   

线性渐变的方向参数:

Delphi	微软	说明
LinearGradientModeHorizontal	Horizontal	指定从左到右的渐变。
LinearGradientModeVertical	Vertical	指定从上到下的渐变。
LinearGradientModeForwardDiagonal	ForwardDiagonal	指定从左上到右下的渐变。
LinearGradientModeBackwardDiagonal	BackwardDiagonal	指定从右上到左下的渐变。

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