再学 GDI+[24]: TGPLinearGradientBrush - 之三

TGPLinearGradientBrush.Create(

  const point1, point2: TGPPoint; {线性渐变起始点与终止点}

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

);



TGPLinearGradientBrush.Create(

  const point1, point2: TGPPointF;

  color1, color2: TGPColor

);


 
   

本例效果图:

---

代码文件:

---

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.


 
   

窗体文件:

---

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