再学GDI+[22]: TGPLinearGradientBrush

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:

代码文件: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.