WinAPI: InvertRgn - 区域颜色取反

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, ExtCtrls;

type
  TForm1 = class(TForm)
    CheckBox1: TCheckBox;
    ColorListBox1: TColorListBox;
    procedure FormPaint(Sender: TObject);
    procedure ColorListBox1Click(Sender: TObject);
    procedure CheckBox1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  Repaint;
end;

procedure TForm1.ColorListBox1Click(Sender: TObject);
begin
  Self.Color := ColorListBox1.Selected;
end;

procedure TForm1.FormPaint(Sender: TObject);
const
  str = 'A';
var
  Rgn: HRGN;
  x,y: Integer;
begin
  Canvas.Font.Size := 120;
  Canvas.Font.Style := [fsBold];
  SetBkMode(Canvas.Handle, TRANSPARENT);

  x := (ClientWidth - ColorListBox1.Width - Canvas.TextWidth(str)) div 2;
  y := -20;

  {建立路径}
  BeginPath(Canvas.Handle);
  Canvas.TextOut(x, y, str);
  EndPath(Canvas.Handle);

  {将路径转换为区域}
  Rgn := PathToRegion(Canvas.Handle);

  {区域颜色取反}
  if CheckBox1.Checked then InvertRgn(Canvas.Handle, Rgn);

  {绘制}
  Canvas.Brush.Color := clSilver;
  Canvas.Brush.Style := bsDiagCross;
  FillRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle);
  Canvas.Brush.Color := clRed;
  Canvas.Brush.Style := bsSolid;
  FrameRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle, 1, 1);

  DeleteObject(Rgn);
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 366
  Top = 269
  Caption = 'Form1'
  ClientHeight = 179
  ClientWidth = 239
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesigned
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
  object CheckBox1: TCheckBox
    Left = 32
    Top = 152
    Width = 97
    Height = 25
    Caption = #21306#22495#39068#33394#21462#21453
    TabOrder = 0
    OnClick = CheckBox1Click
  end
  object ColorListBox1: TColorListBox
    Left = 147
    Top = 0
    Width = 92
    Height = 179
    Align = alRight
    ItemHeight = 16
    TabOrder = 1
    OnClick = ColorListBox1Click
  end
end