MFC. How to display a bitmap or a .png file

Lost User

charlieg wrote:

MS' implementation can be subtle.

I have worked with DCs bitmaps, icons etc over many years using MFC, GDI and GDI+, and never had a problem, other than with my own mistakes.

charlieg

Truth in your statement, but I cut my graphics teeth in X-Windows which seemed to be much more logical than MS' implementation.

Charlie Gilley “They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759 Has never been more appropriate.

BigSteve O

It looks like loadBitmap returns NULL. I have no idea as to why though. Do you have a code snippet you can share?

Victor Nijegorodov

BigSteve-O wrote:

It looks like loadBitmap returns NULL. I have no idea as to why though.

According to Docs in [CBitmap Class | Microsoft Learn](https://learn.microsoft.com/en-us/cpp/mfc/reference/cbitmap-class?view=msvc-170#loadbitmap) :

Quote:

If the bitmap identified by lpszResourceName does not exist or if there is insufficient memory to load the bitmap, the function returns 0.

Victor Nijegorodov

You can try to use LoadImage API instesd: [LoadImageA function (winuser.h) - Win32 apps | Microsoft Learn](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-loadimagea)

CPallini

I used the sample code of this page: CDC Class - CDC::CreateCompatibleDC | Microsoft Learn[^].

"In testa che avete, Signor di Ceprano?" -- Rigoletto

BigSteve O

Thank You. I copied the sample code over, and I have noticed the following: 1) If I draw the bitmap first, and then draw the board afterwards, I can see the board and the test bitmap. 2) If I draw the board first and then the test bitmap, I only see the board. The loadBitmap call is successfull)

charlieg

You still sucking air? I'm coming up on some free time. Turn on your profile to allow direct email.

Charlie Gilley “They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759 Has never been more appropriate.

CPallini

That's rather strange. Do you use the same DC for the board and bitmap?

"In testa che avete, Signor di Ceprano?" -- Rigoletto

charlieg

Okay, you have an error in your code: // Copy the bits from the memory DC into the current dc pDC->BitBlt(20, 10, 436, 364, &MemDCLady, 0, 0, SRCCOPY); is the culprit. Recall that you've set your coordinate system to low English which fixes the bassackwardness of drawing. If you trace your board generation, you will see that your Y values go from 0 to negative values. Looking at the above line, you are drawing off the top of your view window. Change the 364 to -364 and you'll see your image. Of course, *I've* never done that :)

Charlie Gilley “They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759 Has never been more appropriate.

charlieg

See my other reply.

Charlie Gilley “They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759 Has never been more appropriate.

BigSteve O

Yes, I do.

Lost User

Post the complete contents of both your [WM_PAINT](https://learn.microsoft.com/en-us/windows/win32/gdi/wm-paint) and [WM_ERASEBKGND](https://learn.microsoft.com/en-us/windows/win32/winmsg/wm-erasebkgnd). I can help but I need to see both.

BigSteve O

Here is my onDraw()

void CMyChessTestView::OnDraw(CDC* pDC)
{
CMyChessTestDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;

// TODO: add draw code for native data here
// Draw the empty board....
drawImage(pDC, 100, 100);
drawEmptyBoard(pDC);

}

Here is the drawImage(...)

void CMyChessTestView::drawImage(CDC* pDC, int x, int y)
{

// load IDB\_BITMAP1 from our resources
CBitmap bmp;
if (bmp.LoadBitmap(IDB\_LADYPIC))
{
	// Get the size of the bitmap
	BITMAP bmpInfo;
	bmp.GetBitmap(&bmpInfo);

	// Create an in-memory DC compatible with the
	// display DC we're using to paint
	CDC dcMemory;
	
	dcMemory.CreateCompatibleDC(pDC);

	// Select the bitmap into the in-memory DC
	CBitmap \*pOldBitmap = dcMemory.SelectObject(&bmp);

	// Find a centerpoint for the bitmap in the client area
	CRect rect;
	GetClientRect(&rect);
	int nX = rect.left + (rect.Width() - bmpInfo.bmWidth) / 2;
	int nY = rect.top + (rect.Height() - bmpInfo.bmHeight) / 2;

	// Copy the bits from the in-memory DC into the on-
	// screen DC to actually do the painting. Use the centerpoint
	// we computed for the target offset.
	pDC->BitBlt(nX, nY, bmpInfo.bmWidth, bmpInfo.bmHeight, &dcMemory,
		0, 0, SRCCOPY);

	dcMemory.SelectObject(pOldBitmap);
}
else
{
	TRACE0("ERROR: Where's IDB\_LADYPIC?\\n");
}

}

Here is the drawEmptyBoard()

void CMyChessTestView::drawEmptyBoard(CDC* pDC)
{
CMyChessTestDoc* pBC = GetDocument();
ASSERT_VALID(pBC);
if (!pBC)
return;
//drawImage(pDC, 80, 80);
pDC->SetMapMode(MM_LOENGLISH);
pDC->SetWindowExt(800, 800);
//pDC->SetViewportOrg(testrec.Width(), testrec.Height());

for (int i = 0; i < 8; i++)
{
	for (int j = 0; j < 8; j++)
	{
		COLORREF color = pBC->getSquare(i, j);
		CBrush brush(color);
		int x1 = (j \* 70) + 35;
		int y1 = (i \* -70) - 35;
		int x2 = x1 + 70;
		int y2 = y1 - 70;
		CRect rect(x1, y1, x2, y2);
		pDC->FillRect(rect, &brush);
		//pDC->Rectangle(rect);
	}
}
// Now draw the borders
for (int x = 35; x <= 595; x += 70)
{
	pDC->MoveTo(x, -35);
	pDC->LineTo(x, -595);
}
for (int y = -35; y >= -595; y -= 70)
{
	pDC->MoveTo(35, y);
	pDC->LineTo(595, y);
}

Lost User

Really? You draw the chess piece first and then draw the chess board on top of it?

BigSteve O

No, It serves to demonstrate that if I draw the board first, the pieces will not show up, and that by drawing the piece first and then the board, all shows up.

Victor Nijegorodov

BigSteve-O wrote:

if I draw the board first, the pieces will not show up, and that by drawing the piece first and then the board, all shows up.

Then why do you try to draw first the board? :confused:

CPallini

OK, I was able to reproduce your issue, and with a bit of luck, to fix it. The problem arises when you change the DC mapping mode. Now while I am not an expert of mapping modes, this code displays the bitmap over the empty board: Inside OnDraw (is actually OnPaint in my test app)

//..
drawEmptyBoard(&dc);
drawImage(&dc, 105, -105); // note the negative y
//..

While drawImage becomes

/*..*/::drawImage(CDC* pDC, int x, int y)
{
CBitmap bmp;
if (bmp.LoadBitmap(IDB_LADYPIC))
{
BITMAP bmpInfo;
bmp.GetBitmap(&bmpInfo);

	CDC dcMemory;

	dcMemory.CreateCompatibleDC(pDC);
	dcMemory.SetMapMode(pDC->GetMapMode()); // as weird as it looks, the map mode is not the same, after CreateCompatibleDC

	// Select the bitmap into the in-memory DC
	CBitmap\* pOldBitmap = dcMemory.SelectObject(&bmp);

	pDC->StretchBlt(x, y, bmpInfo.bmWidth, bmpInfo.bmHeight, &dcMemory,0, 0, bmpInfo.bmWidth, -bmpInfo.bmHeight, SRCCOPY); // note the negative height of the bitmap

	dcMemory.SelectObject(pOldBitmap);
}

}

To make things more explicit, I would move the SetMapMode call out of drawEmptyBoard.

"In testa che avete, Signor di Ceprano?" -- Rigoletto

BigSteve O

Thank you so much for your suggestions. It is much appreciated! I am going to try it soon.

CPallini

You are welcome.

"In testa che avete, Signor di Ceprano?" -- Rigoletto