再学 GDI+[70]: 路径画刷(10) - SetBlend

本例效果图:

---

代码文件:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, ComCtrls, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    TrackBar1: TTrackBar;

    TrackBar2: TTrackBar;

    TrackBar3: TTrackBar;

    TrackBar4: TTrackBar;

    TrackBar5: TTrackBar;

    TrackBar6: TTrackBar;

    procedure FormPaint(Sender: TObject);

    procedure FormCreate(Sender: TObject);

    procedure TrackBar1Change(Sender: TObject);

    procedure TrackBar2Change(Sender: TObject);

    procedure TrackBar3Change(Sender: TObject);

    procedure TrackBar4Change(Sender: TObject);

    procedure TrackBar5Change(Sender: TObject);

    procedure TrackBar6Change(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



procedure TForm1.FormCreate(Sender: TObject);

begin

  TrackBar1.Max := 10;

  TrackBar2.Max := 10;

  TrackBar3.Max := 10;

  TrackBar4.Max := 10;

  TrackBar5.Max := 10;

  TrackBar6.Max := 10;



  TrackBar1.Position := TrackBar1.Max;

  TrackBar2.Position := TrackBar2.Min;

  TrackBar3.Position := TrackBar3.Max;



  TrackBar4.Position := TrackBar4.Min;

  TrackBar5.Position := TrackBar5.Max div 2;

  TrackBar6.Position := TrackBar6.Max;

end;



procedure TForm1.FormPaint(Sender: TObject);

const

  pts: array[0..2] of TGPPoint = ((X:120; Y:10), (X:40; Y:140), (X:200;Y:140));

  colors: array[0..2] of TGPColor = (aclRed, aclGreen, aclYellow);

var

  g: TGPGraphics;

  path: TGPGraphicsPath;

  pb: TGPPathGradientBrush;

  blendFactors: array[0..2] of Single;

  pos: array[0..2] of Single;

  num: Integer;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  path := TGPGraphicsPath.Create;

  path.AddPolygon(PGPPoint(@pts), Length(pts));



  pb := TGPPathGradientBrush.Create(path);

  num := Length(colors);

  pb.SetSurroundColors(@colors, num); {SetBlend 只在设置包围颜色时有效}



  blendFactors[0] := TrackBar1.Position / 10;

  blendFactors[1] := TrackBar2.Position / 10;

  blendFactors[2] := TrackBar3.Position / 10;

  pos[0] := TrackBar4.Position / 10;

  pos[1] := TrackBar5.Position / 10;

  pos[2] := TrackBar6.Position / 10;



  pb.SetBlend(@blendFactors, Psingle(@pos), Length(blendFactors));

  g.FillPath(pb, path);



  pb.Free;

  path.Free;

  g.Free;

end;



procedure TForm1.TrackBar1Change(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.TrackBar2Change(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.TrackBar3Change(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.TrackBar4Change(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.TrackBar5Change(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.TrackBar6Change(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 222

  ClientWidth = 242

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object TrackBar1: TTrackBar

    Left = 13

    Top = 152

    Width = 105

    Height = 23

    ShowSelRange = False

    TabOrder = 0

    OnChange = TrackBar1Change

  end

  object TrackBar2: TTrackBar

    Left = 13

    Top = 174

    Width = 105

    Height = 23

    ShowSelRange = False

    TabOrder = 1

    OnChange = TrackBar2Change

  end

  object TrackBar3: TTrackBar

    Left = 13

    Top = 196

    Width = 105

    Height = 23

    ShowSelRange = False

    TabOrder = 2

    OnChange = TrackBar3Change

  end

  object TrackBar4: TTrackBar

    Left = 125

    Top = 152

    Width = 105

    Height = 23

    ShowSelRange = False

    TabOrder = 3

    OnChange = TrackBar4Change

  end

  object TrackBar5: TTrackBar

    Left = 125

    Top = 174

    Width = 105

    Height = 23

    ShowSelRange = False

    TabOrder = 4

    OnChange = TrackBar5Change

  end

  object TrackBar6: TTrackBar

    Left = 125

    Top = 196

    Width = 105

    Height = 23

    ShowSelRange = False

    TabOrder = 5

    OnChange = TrackBar6Change

  end

end