再学GDI+[70]: 路径画刷(10)

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.