本例效果圖:
代碼文件: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.
窗體文件:object Form1: TForm1
Left = 0
Top = 0
Caption = 'Form1'
ClientHeight = 206
ClientWidth = 339
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnPaint = FormPaint
PixelsPerInch = 96
TextHeight = 13
object ColorListBox1: TColorListBox
Left = 248
Top = 0
Width = 91
Height = 206
Align = alRight
ItemHeight = 16
TabOrder = 0
OnClick = ColorListBox1Click
end
object TrackBar1: TTrackBar
Left = 0
Top = 184
Width = 249
Height = 45
TabOrder = 1
OnChange = TrackBar1Change
end
end
