再学GDI+[17]: FillRectangle、ColorRefToARGB、TGPSolidBrush

2012-05-05
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导读:本例效果图: 代码文件: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ComCtrls, StdCtr

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)
  ColorListBox1: TColorListBox;
  TrackBar1: TTrackBar;
  procedure FormCreate(Sender: TObject);
  procedure FormPaint(Sender: TObject);
  procedure ColorListBox1Click(Sender: TObject);
  procedure TrackBar1Change(Sender: TObject);
 end;
var
 Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ,GDIPAPI;
procedure TForm1.FormCreate(Sender: TObject);
begin
 Self.Position := poDesktopCenter;
 ColorListBox1.Align := alRight;
 TrackBar1.ShowSelRange := False;
 TrackBar1.PageSize := 20;
 TrackBar1.Min := 0;
 TrackBar1.Max := 255;
 TrackBar1.Position := TrackBar1.Max;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
 g: TGPGraphics;
 r: TGPRect;
 sb: TGPSolidBrush;
 clr: TGPColor;
 Alpha: Byte;
begin
 g := TGPGraphics.Create(Canvas.Handle);
 g.Clear(MakeColor(255,255,255));
 r := MakeRect(20, 20, 200, 150);
 clr := ColorRefToARGB(ColorListBox1.Selected);
 Alpha := TrackBar1.Position;
 clr := MakeColor(Alpha, GetRed(clr), GetGreen(clr), GetBlue(clr));
 sb := TGPSolidBrush.Create(clr);
 g.FillRectangle(sb, r);
 sb.Free;
 g.Free;
end;
procedure TForm1.ColorListBox1Click(Sender: TObject);
begin
 Repaint;
end;
procedure TForm1.TrackBar1Change(Sender: TObject);
begin
 Repaint;
 Text := Format('透明度: %d', [TrackBar1.Position]);
end;
end.

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