From: "Shannon Broskie" <shannonbroskie@tagfolio.com>
Newsgroups: borland.public.delphi.graphics
References: <3ac8ec1a_2@dnews>
Subject: Re: Maskblt - proper way
Date: Thu, 5 Apr 2001 13:21:03 -0400
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Xref: dnews borland.public.delphi.graphics:37035

This is what I wound up doing...  Any suggestions?

procedure DrawTitleBarImage (const Form : TForm; const Bitmap: TBitmap);
var
  Mask : TBitmap;
  FormDC : HDC;
  CyCaption, CxSize, CxDlgFrame, CyDlgFrame, CyEdge, CxEdge, SxIcon, SyIcon
: integer;
  BorderIconCount, ImgLeft, ImgTop : integer;
  FormStyle : int64;
  FormIcons : TBorderIcons;
  ARect : TRect;
begin
  FormDC := GetWindowDC (Form.Handle);

  CyCaption := GetSystemMetrics (SM_CYCAPTION);    // Height of Title bar
  CxSize := GetSystemMetrics (SM_CXSIZE);          // Width of button in
title bar
  CxDlgFrame := GetSystemMetrics (SM_CXDLGFRAME);  // Thickness of frame
  CyDlgFrame := GetSystemMetrics (SM_CYDLGFRAME);  // Thickness of frame
  CxEdge := GetSystemMetrics (SM_CXEDGE);          // 3D border thickness
  CyEdge := GetSystemMetrics (SM_CYEDGE);          // 3D border thickness
  SxIcon := GetSystemMetrics (SM_CXSMICON);        // Recommended icon x
size
  SyIcon := GetSystemMetrics (SM_CYSMICON);        // Recommended icon y
size

  FormStyle := GetWindowLong (Form.Handle, GWL_STYLE);

  FormIcons := Form.BorderIcons;

  // Make sure there's a title bar to draw in...
  if FormStyle and WS_CAPTION = WS_CAPTION then
  begin
    // Check what title bar buttons are shown
    BorderIconCount := 1;
    if biMinimize in FormIcons then
      inc (BorderIconCount);
    if biMaximize in FormIcons then
      inc (BorderIconCount);
    if biSystemMenu in FormIcons then
      inc (BorderIconCount);

    // Resize Bitmap to recommended title bar icon sizes
    ARect := Rect (0, 0, SxIcon, SyIcon);
    Bitmap.Canvas.StretchDraw (ARect, Bitmap);

    // Calculate left and top starting point of image
    ImgLeft := Form.Width - (BorderIconCount * CxSize + CxDlgFrame +
CxEdge);
    ImgTop := (CyCaption + CyDlgFrame + CyEdge - Bitmap.Height) div 2;

    Mask := TBitmap.Create;
    Mask.Assign (Bitmap);
    Mask.Mask(Bitmap.TransparentColor);
    try
      TransparentStretchBlt (FormDC, ImgLeft, ImgTop, Bitmap.Width,
Bitmap.Height,
                             Bitmap.Canvas.Handle, 0, 0, Bitmap.Width,
Bitmap.Height,
                             Mask.Canvas.Handle, 0, 0);
    finally
      Mask.Free;
    end;
  end;
end;


"Shannon Broskie" <shannonbroskie@tagfolio.com> wrote in message
news:3ac8ec1a_2@dnews...
> What is the proper way to transparently draw a bitmap?
>
> I need to use Maskblt because the final image will wind up being in the
> form's title bar.
>
> I'm having trouble generating the mask...
> Here's some code I've been using to play around with it...
>
> var
>   DC : HDC;
> begin
>   image1.Picture.Bitmap.Assign (imgLock.Picture.Bitmap);
>   image1.Picture.Bitmap.Mask (imgLock.Picture.Bitmap.TransparentColor);
>   DC := GetWindowDC (Self.Handle);
>   MaskBlt (DC, 100, 100, imgLock.Width, imgLock.Height,
> imgLock.Canvas.Handle, 0, 0,
>            image1.Canvas.Handle, 0, 0, SRCCOPY);
>
>
> The mask method of image1 seems to generate a mask that maskblt does not
> like...  Any ideas?
>
> Thanks in advance...
>
>