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:

unit Unit1;interfaceusesWindows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs, StdCtrls, TeCanvas;typeTForm1 = 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;varForm1: TForm1;implementation{$R *.dfm}uses GDIPOBJ, GDIPAPI, TypInfo;procedure TForm1.FormCreate(Sender: TObject);
vari: Integer;
beginfor i := 0 to 3 doComboBox1.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);
varg: TGPGraphics;lb: TGPLinearGradientBrush;c1,c2: TGPColor;r: TGPRect;
beging := 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);
beginRepaint;
end;procedure TForm1.ButtonColor2Click(Sender: TObject);
beginRepaint;
end;procedure TForm1.ComboBox1Change(Sender: TObject);
beginRepaint;
end;end.

窗体文件:

object Form1: TForm1Left = 0Top = 0Caption = 'Form1'ClientHeight = 197ClientWidth = 309Color = clBtnFaceFont.Charset = DEFAULT_CHARSETFont.Color = clWindowTextFont.Height = -11Font.Name = 'Tahoma'Font.Style = []OldCreateOrder = FalsePosition = poScreenCenterOnCreate = FormCreateOnPaint = FormPaintPixelsPerInch = 96TextHeight = 13object ComboBox1: TComboBoxLeft = 113Top = 6Width = 192Height = 21ItemHeight = 13TabOrder = 0Text = 'ComboBox1'OnChange = ComboBox1Changeendobject ButtonColor1: TButtonColorLeft = 5Top = 4Width = 49Caption = 'ButtonColor1'TabOrder = 1OnClick = ButtonColor1Clickendobject ButtonColor2: TButtonColorLeft = 58Top = 4Width = 49Caption = 'ButtonColor2'TabOrder = 2OnClick = ButtonColor2Clickend
end

线性渐变的方向参数: