再学 GDI+[68]: 路径画刷(8) SetBlendTriangularShaped、SetBlendBellShape

本例效果图(颜色失真严重, 因为 GIF 最多只能接受 256 中颜色):

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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;
    RadioGroup1: TRadioGroup;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure RadioGroup1Click(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
    procedure TrackBar2Change(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormCreate(Sender: TObject);
begin
  TrackBar1.Max := 100;
  TrackBar2.Max := 100;
  TrackBar1.Position := TrackBar1.Max;
  TrackBar2.Position := TrackBar2.Max;
  TrackBar1.ShowSelRange := False;
  TrackBar2.ShowSelRange := False;
  TrackBar1.Height := 23;
  TrackBar2.Height := 23;

  RadioGroup1.Items.CommaText := 'BlendTriangularShape, SetBlendBellShape';
  RadioGroup1.ItemIndex := 0;

  DoubleBuffered := True;
end;

procedure TForm1.FormPaint(Sender: TObject);
const
  colors: array[0..0] of TGPColor = (aclRed);
var
  g: TGPGraphics;
  path: TGPGraphicsPath;
  pb: TGPPathGradientBrush;
  num: Integer;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  path := TGPGraphicsPath.Create;
  path.AddRectangle(MakeRect(30,10,160,150));
  pb:= TGPPathGradientBrush.Create(path);

  num := Length(colors);
  pb.SetSurroundColors(@colors, num);

  pb.SetCenterColor(aclYellow);

  {SetBlendTriangularShape 与 SetBlendBellShape 参数2的默认值都是 1.0}
  case RadioGroup1.ItemIndex of
    0: pb.SetBlendTriangularShape(TrackBar1.Position/100, TrackBar2.Position/100);
    1: pb.SetBlendBellShape(TrackBar1.Position/100, TrackBar2.Position/100);
  end;

  g.FillPath(pb, path);

  pb.Free;
  path.Free;
  g.Free;
end;

procedure TForm1.RadioGroup1Click(Sender: TObject);
begin
  Repaint;
end;

procedure TForm1.TrackBar1Change(Sender: TObject);
begin
  Repaint;
end;

procedure TForm1.TrackBar2Change(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

---

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 261
  ClientWidth = 221
  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 = 0
    Top = 167
    Width = 113
    Height = 45
    TabOrder = 0
    OnChange = TrackBar1Change
  end
  object TrackBar2: TTrackBar
    Left = 108
    Top = 167
    Width = 113
    Height = 45
    TabOrder = 1
    OnChange = TrackBar2Change
  end
  object RadioGroup1: TRadioGroup
    Left = 8
    Top = 192
    Width = 206
    Height = 61
    Caption = 'RadioGroup1'
    TabOrder = 2
    OnClick = RadioGroup1Click
  end
end