再学 GDI+[61]: 路径画刷(1) SetCenterColor、SetSurroundColors

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, StdCtrls, CheckLst, ExtCtrls, TeCanvas;

type
  TForm1 = class(TForm)
    ButtonColor1: TButtonColor;
    ButtonColor2: TButtonColor;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure ButtonColor1Click(Sender: TObject);
    procedure ButtonColor2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormCreate(Sender: TObject);
begin
  ButtonColor1.Caption := '中心色    ';
  ButtonColor2.Caption := '周边色    ';
  ButtonColor1.SymbolColor := clLime;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  rect: TGPRect;
  path: TGPGraphicsPath;
  pb: TGPPathGradientBrush;
  ColorArr: array[0..0] of TGPColor;
  num: Integer;
begin
  rect := MakeRect(20, 10, ClientWidth - 40, ClientHeight - 50);
  g := TGPGraphics.Create(Canvas.Handle);
  path := TGPGraphicsPath.Create;
  path.AddEllipse(rect);

  pb := TGPPathGradientBrush.Create(path);
  pb.SetCenterColor(ColorRefToARGB(ButtonColor1.SymbolColor));

  ColorArr[0] := ColorRefToARGB(ButtonColor2.SymbolColor);
  num := 1;
  pb.SetSurroundColors(PARGB(@ColorArr), num);

  g.FillEllipse(pb, rect);

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

procedure TForm1.ButtonColor1Click(Sender: TObject);
begin
  Repaint;
end;

procedure TForm1.ButtonColor2Click(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 258
  ClientWidth = 208
  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 ButtonColor1: TButtonColor
    Left = 24
    Top = 225
    Caption = 'ButtonColor1'
    TabOrder = 0
    OnClick = ButtonColor1Click
  end
  object ButtonColor2: TButtonColor
    Left = 112
    Top = 225
    Caption = 'ButtonColor2'
    TabOrder = 1
    OnClick = ButtonColor2Click
  end
end