再学 GDI+[65]: 路径画刷(5) SetGammaCorrection

本例效果图:

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代码文件:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormPaint(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormPaint(Sender: TObject);
const
  ColorArr: array[0..2] of TGPColor = (aclRed, aclGreen, aclBlue);
var
  pts: array[0..2] of TGPPoint;
  g: TGPGraphics;
  path: TGPGraphicsPath;
  pb: TGPPathGradientBrush;
  num: Integer;
begin
  pts[0] := MakePoint(80, 10);
  pts[1] := MakePoint(10, 150);
  pts[2] := MakePoint(150, 150);

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

  path := TGPGraphicsPath.Create;
  path.AddPolygon(PGPPoint(@pts), Length(pts));
  //pb := TGPPathGradientBrush.Create(path); {这样建立中心默认白色; 按下一句中心默认黑色}
  pb := TGPPathGradientBrush.Create(PGPPoint(@pts), Length(pts)); {根据点数组建立路径画刷}
  pb.SetCenterColor(aclWhite);
  num := Length(pts);
  pb.SetSurroundColors(PARGB(@ColorArr), num);
  g.FillPath(pb, path);

  {使用灰度校正模式换个地方再画一次}
  pb.SetGammaCorrection(True);
  g.TranslateTransform(150, 0);
  g.FillPath(pb, path);

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

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 163
  ClientWidth = 311
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
end