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