Re: Bitmap continued

From:

Ed <me@right.her>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 10 Jan 2011 20:43:04 -0500

Message-ID:

<HKGdnehQRJk8KLbQnZ2dnUVZ_jqdnZ2d@giganews.com>

I need to scale the image to fit within the boundries of the picture
control.

On 1/10/2011 8:28 PM, Joseph M. Newcomer wrote:

Note that when you are drawing using the PaintDC for a child control, the DC area
encompasses as much of the parent area as is available. Therefore, you have to set a
clipping region to limit the drawing, or use StretchBlt to the client area of the control.

This is an ancient bug, unfortunately, and was based on some bizarre notion of improving
performance on an 8088 with a CGA display. Now the excuse is that if it is changed, it
will "break" the existing badly broken behavior!

The code to do this is:

CPaintDC dc(this); // this is the name of the DC

CRect r;
GetClientRect(&r);

CRgn rgn;
rgn.CreateRectRgn(r.left, r.top, r.right, r.bottom);
dc.SelectClipRgn(&rgn);

Be sure the DC is restored before you leave the scope where the CRgn is declared so it is
no longer selected.
joe

On Mon, 10 Jan 2011 19:08:13 -0500, Ed<me@right.her> wrote:

I found several errors myself while awaiting your answer as you saw in
my 2nd reply.
Now the bitmap displays BUT it is not within the picture window.
The upper left is within my picture box but the image goes way beyond
the bottom and right of the ShowBmp box.

On 1/10/2011 4:52 PM, Joseph M. Newcomer wrote:

On Mon, 10 Jan 2011 15:05:54 -0500, Ed<me@right.her> wrote:

I am down to two errors during build...

HBITMAP bmp = ::LoadImage(AfxGetInstanceHandle(), filename,
IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | LR_SHARED);

error C2440: 'initializing' : cannot convert from 'void *' to 'struct
HBITMAP__ *'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast
=====================================================================
dc.FillSolidRect(&r,&br);

error C2664: 'void __thiscall CDC::FillSolidRect(const struct tagRECT
*,unsigned long)'
cannot convert parameter 2 from 'class CBrush *' to 'unsigned long'
This conversion requires a reinterpret_cast, a C-style cast or
function-style cast
=====================================================================

****
This is pretty elementary C programming, something you really shouldl have figured out on
your own. A cast is required, as I pointed out in my reply in the earlier thread. I'm
very surprised you couldn't figure out something this simple.
****

I still would like to know where the bitmap selection comes in.

void CShowBmp::OnPaint()
{
    CPaintDC dc(this);

    int filenumber;
// ... formulate filename here, based on the ID
// Example: Files are found in the project's executable directory
    CString t;
    LPTSTR p = t.GetBuffer(MAX_PATH);
    ::GetModuleFileName(NULL, p, MAX_PATH);
    p=_tcsrchr(p, _T('\\'));
    if(p == NULL)
    { /* not possible */
      ASSERT(FALSE);
      t.ReleaseBuffer();
      return;
    } /* not possible */
    ++p;
    *p = _T('\0');
    t.ReleaseBuffer();

    CString filename;
    filename.Format(_T("%s%02d.bmp"), filename, filenumber);

****
My error; this should have said
filename.Format(_T("%s%02d.bmp"), t, filenumber);
I changed the name and didn't catch all the uses.
****

    HBITMAP bmp = ::LoadImage(AfxGetInstanceHandle(), filename,
IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | LR_SHARED);

    // Depending on what I am doing, I might add LR_LOADMAP3DCOLORS or
LR_LOADTRANSPARENT
    if(bmp == NULL)
    { /* failed to load */
      CRect r;
      GetClientRect(&r);

      // Define an error brush. To make it invisible, you might use
      // a solid brush of ::GetSysColor(COLOR_3DFACE)
      // or a hatched brush
      // For a hatched brush, I might set a dark background color

      CBrush br(HS_DIAGCROSS, RGB(0,0,0));
      dc.SetBkColor(RGB(96, 96, 96));

      // This can be recognized as the indication of a failure

      dc.FillSolidRect(&r,&br);

      return;
    } /* failed to load */

    CBitmap bm;
    bm.Attach(bmp);
    BITMAP bmd;
    bm.GetBitmap(&bmd);

    CDC MemDC;
    MemDC.CreateCompatibleDC(&dc);

    int save = MemDC.SaveDC();
    MemDC.SelectObject(&bm);
    // I could use BitBlt or StretchBlt; I;m showing BitBlt below
    dc.BitBlt(0, 0, bmd.bmWidth, bmd.bmHeight,&MemDC, 0,0, SRCCOPY);
    MemDC.RestoreDC(save);
}

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm