再学 GDI+[70]: 路径画刷(10) - SetBlend

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.

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