再學 GDI+[24]: TGPLinearGradientBrush - 之三

TGPLinearGradIEntBrush.Create(
　const point1, point2: TGPPoint; {線性漸變起始點與終止點}
　color1, color2: TGPColor　　　　{線性漸變起始色與終止色}
);
TGPLinearGradIEntBrush.Create(
　const point1, point2: TGPPointF;
　color1, color2: TGPColor
);本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, TeCanvas, ExtCtrls;
type
　TForm1 = class(TForm)
　　ButtonColor1: TButtonColor;
　　ButtonColor2: TButtonColor;
　　procedure FormCreate(Sender: TObject);
　　procedure FormPaint(Sender: TObject);
　　procedure ButtonColor1Click(Sender: TObject);
　　procedure ButtonColor2Click(Sender: TObject);
　　procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
　　　Shift: TShiftState; X, Y: Integer);
　　procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
　　　Shift: TShiftState; X, Y: Integer);
　　procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI, TypInfo;
var
　pts: array[0..1] of TPoint;
　f: Boolean;
　p: 0..2;
procedure TForm1.FormCreate(Sender: TObject);
begin
　ButtonColor1.Caption := '色1　　 ';
　ButtonColor2.Caption := '色2　　 ';
　ButtonColor1.SymbolColor := clLime;
　ButtonColor2.SymbolColor := clBlack;
　pts[0].X := 8;
　pts[0].Y := 8;
　pts[1].X := ClIEntWidth - 10;
　pts[1].Y := ClIEntHeight - 10;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
　lb: TGPLinearGradIEntBrush;
　c1,c2: TGPColor;
　r: TGPRect;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(aclRed);
　r := MakeRect(20, 40, ClientWidth - 40, ClIEntHeight - 50);
　c1 := ColorRefToARGB(ButtonColor1.SymbolColor);
　c2 := ColorRefToARGB(ButtonColor2.SymbolColor);
　lb := TGPLinearGradIEntBrush.Create(TGPPoint(pts[0]), TGPPoint(pts[1]), c1, c2);
　g.FillEllipse(lb, r);
　g.DrawRectangle(p, MakeRect(pts[0].X-2, pts[0].Y-2, 4, 4));
　g.DrawRectangle(p, MakeRect(pts[1].X-2, pts[1].Y-2, 4, 4));
　lb.Free;
　p.Free;
　g.Free;
end;
procedure TForm1.ButtonColor1Click(Sender: TObject);
begin
　Repaint;
end;
procedure TForm1.ButtonColor2Click(Sender: TObject);
begin
　Repaint;
end;
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　f := True;
end;
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
　Y: Integer);
var
　i: Integer;
begin
　if f then
　begin
　　if p = 0 then Exit;
　　pts[p-1] := Point(X,Y);
　　Repaint;
　end else begin
　　p := 0;
　　Cursor := crDefault;
　　for i := 0 to 1 do
　　　if PtInRect(Bounds(pts[i].X-2, pts[i].Y-2, 4, 4), Point(X,Y)) then
　　　begin
　　　　p := i+1;
　　　　Cursor := crHandPoint;
　　　end;
　end;
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　f := False;
end;
end.窗體文件: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
　OnMouseDown = FormMouseDown
　OnMouseMove = FormMouseMove
　OnMouseUp = FormMouseUp
　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
end