Delphi 與 DirectX 之 DelphiX(12): TPictureCollectionItem.DrawAlpha

本例:

代碼檔案:

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, DXDraws, StdCtrls, DXClass, ComCtrls;type  TForm1 = class(TForm)    DXDraw1: TDXDraw;    DXImageList1: TDXImageList;    TrackBar1: TTrackBar;    procedure FormCreate(Sender: TObject);    procedure TrackBar1Change(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}var  PicItem: TPictureCollectionItem;procedure TForm1.FormCreate(Sender: TObject);const  ImgPath1 = 'C:\Temp\DelphiX.bmp';begin  DXImageList1.DXDraw := DXDraw1;  PicItem := TPictureCollectionItem(DXImageList1.Items.Add);  PicItem.Picture.LoadFromFile(ImgPath1);  TrackBar1.Max := 255;  TrackBar1.Min := 0;  TrackBar1.Height := 22;  TrackBar1.ShowSelRange := False;  TrackBar1.Align := alBottom;end;procedure TForm1.TrackBar1Change(Sender: TObject);var  r: TRect;begin  r := Bounds((DXDraw1.Width - PicItem.Width) div 2,              (DXDraw1.Height - PicItem.Height) div 2,               PicItem.Width,               PicItem.Height);  DXDraw1.Surface.Fill(0);  PicItem.DrawAlpha(DXDraw1.Surface, r, 0, TrackBar1.Position);  DXDraw1.Flip;end;end.