再學GDI+[22]: TGPLinearGradientBrush - 之一: TLinearGradien

TGPLinearGradientBrush.Create(
　rect: TGPRect;　　　　　　{線性漸變的界限}
　color1, color2: TGPColor; {線性漸變起始色與終止色}
　mode: TLinearGradientMode {漸變方向, 見下表}
);
TGPLinearGradientBrush.Create(
　rect: TGPRectF;
　color1, color2: TGPColor;
　mode: TLinearGradientMode
);

本例效果圖:

代碼文件: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.

窗體文件: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

線性漸變的方向參數:

Delphi 微軟 說明 LinearGradientModeHorizontal Horizontal 指定從左到右的漸變。 LinearGradientModeVertical Vertical 指定從上到下的漸變。 LinearGradientModeForwardDiagonal ForwardDiagonal 指定從左上到右下的漸變。 LinearGradientModeBackwardDiagonal BackwardDiagonal 指定從右上到左下的漸變。