TImgEdit控件上放透明Panel

Question

描述；在TImgEdit控件上放一个TRzPanel，设置TRzPanel为透明.TImgEdit载入tif图象文件后，TRzPanel并没有透明；拖动TImgEdit的滚动条，TRzPanel也没有透明。问题：在TImgEdit控件上放置一个什么样的Panel，可以使这个Panel透明显示TImgEdit控件载入的tif图象。谢谢！！！

Answer 1

{******************************************************************************}
{ @UnitName     : uTransPanel,pas                                              }
{ @Author       : Budded                                                       }
{ @Description  : 透明 Panel                                                   }
{ @FileVersion  : 1.0.0.0                                                      }
{ @CreateDate   : 2005-08-24                                                   }
{ @LastUpdate   : Budded, 2005-08-24                                           }
{ @History      : Created By Budded, 2005-08-24 10:20                          }
{******************************************************************************}
unit uTransPanel;interfaceuses
  Windows, Messages, SysUtils, Graphics, Classes, Controls, ExtCtrls, Buttons;type
  TTransMode = (tmNone, tmSRCCOPY, tmSRCPAINT, tmSRCAND, tmSRCINVERT, tmSRCERASE,
    tmNOTSRCCOPY, tmNOTSRCERASE, tmMERGECOPY, tmMERGEPAINT,
    tmPATCOPY, tmPATPAINT, tmPATINVERT, tmDSTINVERT, tmBLACKNESS, tmWHITENESS);  TTransPanel = class(TPanel)
  private
    { Private declarations }
    FTransMode: TTransMode;    procedure CMCtl3DChanged(var Message: TMessage); message CM_CTL3DCHANGED;
    procedure WMEraseBkgnd(var Message: TMessage); message WM_ERASEBKGND;
    procedure WMWindowPosChanging(var Message: TWMWindowPosChanging); message WM_WINDOWPOSCHANGING;
    function GetTransModeEx: Integer;
  protected
    { Protected declarations }
    Buffer: TBitmap;
    procedure CreateParams(var Params: TCreateParams); override;
    procedure Paint; override;
    procedure Resize; override;
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
    destructor Destroy(); override;
    property TransModeEx: Integer read GetTransModeEx;
  published
    { Published declarations }
    property TransMode: TTransMode read FTransMode write FTransMode default tmSRCCOPY;
  end;procedure Register;implementationprocedure Register;
begin
  RegisterComponents('Budded', [TTransPanel]);
end;{ TTransPanel }procedure TTransPanel.CMCtl3DChanged(var Message: TMessage);
begin
  inherited;
  RecreateWnd;
end;constructor TTransPanel.Create(AOwner: TComponent);
begin
  inherited;
  Buffer := TBitmap.Create;
  FTransMode := tmSRCCOPY;
end;procedure TTransPanel.CreateParams(var Params: TCreateParams);
begin
  inherited;
  Params.ExStyle := Params.ExStyle + WS_EX_TRANSPARENT;
end;destructor TTransPanel.Destroy;
begin
  if Assigned(Buffer) then
    Buffer.Free;
  inherited;
end;function TTransPanel.GetTransModeEx: Integer;
begin
  Result := 0;
  case TransMode of  //case
    tmNone: Result := 0;
    tmSRCCOPY: Result := SRCCOPY;
    tmSRCPAINT: Result := SRCPAINT;
    tmSRCAND: Result := SRCAND;
    tmSRCINVERT: Result := SRCINVERT;
    tmSRCERASE: Result := SRCERASE;
    tmNOTSRCCOPY: Result := NOTSRCCOPY;
    tmNOTSRCERASE: Result := NOTSRCERASE;
    tmMERGECOPY: Result := MERGECOPY;
    tmMERGEPAINT: Result := MERGEPAINT;
    tmPATCOPY: Result := PATCOPY;
    tmPATPAINT: Result := PATPAINT;
    tmPATINVERT: Result := PATINVERT;
    tmDSTINVERT: Result := DSTINVERT;
    tmBLACKNESS: Result := BLACKNESS;
    tmWHITENESS: Result := WHITENESS;
  end;  // end case
end;procedure TTransPanel.Paint;
var
  Rect: TRect;
  TopColor, BottomColor: TColor;  procedure AdjustColors(Bevel: TPanelBevel);
  begin
    TopColor := clBtnHighlight;
    if Bevel = bvLowered then TopColor := clBtnShadow;
    BottomColor := clBtnShadow;
    if Bevel = bvLowered then BottomColor := clBtnHighlight;
  end;begin
//  inherited;  Rect := ClientRect;//Rect(0, 0, Width, Height);
  Buffer.Width := Width;
  Buffer.Height := Height;
  Buffer.Canvas.Brush.Style := bsSolid;
  Buffer.Canvas.Brush.Color := Color;
  Buffer.Canvas.FillRect(Rect);
  StretchBlt(Buffer.Canvas.Handle, 0, 0, Width, Height,
    Canvas.Handle, 0, 0, Width, Height, TransModeEx);  if Ctl3D then DrawEdge(Buffer.Canvas.Handle, Rect, BDR_RAISEDINNER, BF_RECT);  if BevelOuter <> bvNone then
  begin
    AdjustColors(BevelOuter);
    Frame3D(Buffer.Canvas, Rect, TopColor, BottomColor, BevelWidth);
  end;
  if BevelInner <> bvNone then
  begin
    AdjustColors(BevelInner);
    Frame3D(Buffer.Canvas, Rect, TopColor, BottomColor, BevelWidth);
  end;  Buffer.Canvas.Pen.Mode := pmCopy;
  Buffer.Canvas.Pen.Style := psSolid;  Canvas.Draw(0, 0, Buffer);
end;procedure TTransPanel.Resize;
begin
  inherited;
end;procedure TTransPanel.WMEraseBkgnd(var Message: TMessage);
begin
  Message.Result := 0;
end;procedure TTransPanel.WMWindowPosChanging(var Message: TWMWindowPosChanging);
begin
  Invalidate;
  inherited;
end;end.
唉，还是好几年前的东西了，