一个用UpdateLayeredWindow实现窗体半透明的delphi的代码

http://www.pudn.com/downloads171/sourcecode/windows/detail791686.html

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, gdipapi, gdipobj, Menus, StdCtrls;

type
TForm1 = class(TForm)
    PopupMenu1: TPopupMenu;
    ChangeSkin1: TMenuItem;
    N1: TMenuItem;
    Close1: TMenuItem;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure ShowPNGForm1(PNGFile:string; nTran: integer);
    procedure ShowPNGForm2(PNGFile:string; nTran: integer);
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Close1Click(Sender: TObject);
    procedure ChangeSkin1Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
private
    { Private declarations }
public
    { Public declarations }
end;

const
WS_EX_LAYERED = $80000;
LWA_COLORKEY = 1;
LWA_ALPHA     = 2;
ULW_COLORKEY = 1;
ULW_ALPHA     = 2;
ULW_OPAQUE    = 4;

var
Form1: TForm1;
bmp, old_bmp : HBITMAP;
DC : HDC;
bitmap: tgpbitmap;
j:integer;

Function UpdateLayeredWindow(hWnd : HWND;
                            hdcDst : HDC; pptDst : PPoint; psize : PSize;
                            hdcSrc : HDC; pptSrc : PPoint;
                            crKey : COLORREF;
                            pblend : PBlendFunction;
                            dwFlags : DWORD): BOOL; stdcall;

implementation

{$R *.dfm}

Function UpdateLayeredWindow; external 'user32.dll';

procedure Tform1.ShowPNGForm1(PNGFile:string; nTran: integer);
var
graphics : TGPGraphics;
Image: TGPImage;

begin

graphics := TGPGraphics.Create(DC);
Image:= TGPImage.Create(PNGFile);

graphics.DrawImage(image, 0, 0);
//UpdateLayeredWindow(Handle, Canvas.Handle, @pt1, @sz, DC, @pt2,0, @bf,ULW_ALPHA);
end;

procedure Tform1.ShowPNGForm2(PNGFile:string; nTran: integer);
var
pt1, pt2 : TPoint;
sz : TSize;
bf : TBlendFunction;
begin

bitmap:=tgpbitmap.Create(PNGFile);
pt1 := Point(left,top); //窗口做上角的坐标
pt2 := Point(0, 0); //这个就不用说了，一看见（0，0）就应该明白了
sz.cx := bitmap.GetWidth; //尺寸不要超过图像大小，不然窗口就什么都没有了，连个影子都没有
sz.cy := bitmap.GetHeight; //同上
bf.BlendOp := AC_SRC_OVER; //这些死记就行了
bf.BlendFlags := 0;                  //同上
if (nTran<0) or (nTran>255) then nTran:=255;
bf.SourceConstantAlpha := nTran; //同上
bf.AlphaFormat := AC_SRC_ALPHA; //同上

DeleteObject(bmp); //前面就是在这里犯的错误，不然占用的内存会无限增大
bitmap.GetHBITMAP(0,bmp); // HBITMAP是windows标准位图格式，支持透明，这里是从tgpbitmap 转化成 HBITMAP
DeleteDC(DC);
DC := CreateCompatibleDC(Canvas.Handle); //API的含义我倒是明白，为什么写这句话我就不明白了，反正就是需要
old_bmp := SelectObject(DC, bmp); //同上
UpdateLayeredWindow(Handle, Canvas.Handle, @pt1, @sz, DC, @pt2,0, @bf,ULW_ALPHA);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
if SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYERED) = 0 then ShowMessage(SysErrorMessage(GetLastError));

ShowPNGForm2('test.png',255);
J:=1;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
SelectObject(DC, old_bmp);
DeleteObject(bmp);
DeleteDC(DC);
bitmap.Free;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
if(Button = mbLeft) then
    begin
      ReleaseCapture();
      Perform(WM_SYSCOMMAND, SC_MOVE or HTCAPTION, 0);
    end;
end;

procedure TForm1.Close1Click(Sender: TObject);
begin
Close;
end;

procedure TForm1.ChangeSkin1Click(Sender: TObject);
var
dlgOpen: TOpenDialog;
begin
dlgOpen := TOpenDialog.Create(Self);
dlgOpen.Filter := 'PNG file(*.png)|*.png';
if(dlgOpen.Execute()) then
    begin
      ShowPNGForm2(dlgOpen.FileName,255);
    end;
dlgOpen.Free;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage('aaa');
end;

end.

--------------------------------------------------

object Form1: TForm1
Left = 387
Top = 124
BorderStyle = bsNone
Caption = 'Form1'
ClientHeight = 165
ClientWidth = 260
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
PopupMenu = PopupMenu1
OnCreate = FormCreate
OnDestroy = FormDestroy
OnMouseDown = FormMouseDown
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
    Left = 104
    Top = 56
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
end
object PopupMenu1: TPopupMenu
    Left = 16
    Top = 16
    object ChangeSkin1: TMenuItem
      Caption = 'ChangeSkin'
      OnClick = ChangeSkin1Click
    end
    object N1: TMenuItem
      Caption = '-'
    end
    object Close1: TMenuItem
      Caption = 'Close'
      OnClick = Close1Click
    end
end
end

//背景穿透（相当于锁定桌面）
procedure TForm1.N3Click(Sender: TObject);
begin
SetWindowLong(Self.Handle,
GWL_EXSTYLE,
GetWindowLong(Self.Handle,GWL_EXSTYLE) or WS_EX_TRANSPARENT);
Application.MessageBox('你已关闭不了程序了，请从任务管理器里关闭',
'提示',MB_OK or MB_ICONINFORMATION);
end;

http://www.cnblogs.com/-clq/archive/2012/08/22/2650705.html