C / C++ / MFC

Re: Having difficulty writing text on a bitmap [modified]

26-Nov-08 16:19

I am facing problems trying to write text onto a bitmap in the hopes of getting pixelated text on it.

I have looked at the code shown here: <ahref>http://www.codeproject.com/KB/GDI/gdionbitmaps.aspx[^]
but I can't seem to get it to work right.

Here's my code, I am using the code shown on the above site and triggering it to run on a button click form a dialog:

void CCaptureAndDisplayDlg::OnTest() 
{

	HBITMAP hbitmap = ::LoadBitmap(AfxGetInstanceHandle(), MAKEINTRESOURCE(IDB_BITMAP1));
	BITMAP bitm;
	GetObject( hbitmap, sizeof(BITMAP), &bitm );
	long width=bitm.bmWidth;
	long height=bitm.bmHeight;
	BITMAPINFO bmInfo;

	memset(&bmInfo.bmiHeader,0,sizeof(BITMAPINFOHEADER));
	bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
	bmInfo.bmiHeader.biWidth=width;
	bmInfo.bmiHeader.biHeight=height;
	bmInfo.bmiHeader.biPlanes=1;
	bmInfo.bmiHeader.biBitCount=24;

	//create a temporary dc in memory.
	HDC pDC = ::GetDC(0);
	HDC TmpDC=CreateCompatibleDC(pDC);

	//create a new bitmap and select it in the memory dc
	BYTE *pbase;
	HBITMAP TmpBmp=CreateDIBSection(pDC, &bmInfo,DIB_RGB_COLORS,(void**)&pbase,0,0);
	HGDIOBJ TmpObj=SelectObject(TmpDC,TmpBmp);

	//draw the background
	HDC dcBmp=CreateCompatibleDC(TmpDC);
	HGDIOBJ TmpObj2 = SelectObject(dcBmp,hbitmap);
	BitBlt(TmpDC,0,0,width,height,dcBmp,0,0,SRCCOPY);
	SelectObject(TmpDC,TmpObj2);
	DeleteDC(dcBmp);

	//choose the font
	CFont m_Font;
	LOGFONT* m_pLF;
	m_pLF=(LOGFONT*)calloc(1,sizeof(LOGFONT));
	strncpy(m_pLF->lfFaceName,"Times New Roman",31);
	m_pLF->lfHeight=64;
	m_pLF->lfWeight=400;
	m_pLF->lfItalic=0;
	m_pLF->lfUnderline=0;
	m_Font.CreateFontIndirect(m_pLF);

	//select the font in the dc
	CDC dc;
	dc.Attach(TmpDC);
	CFont* pOldFont=NULL;
	if (m_Font.m_hObject) 
		pOldFont = dc.SelectObject(&m_Font);
	else 
		dc.SelectObject(GetStockObject(DEFAULT_GUI_FONT));

	//Set text color
	dc.SetTextColor(RGB(0,0,0));		//Black Pen

	//Set text position;

	RECT pos = {40,40,0,0};

	//draw the text
	dc.SetBkMode(TRANSPARENT);

	dc.DrawText(strTxt,TxtLen,&pos,DT_CALCRECT);
	dc.DrawText(strTxt,TxtLen,&pos,0);

	m_Placemat.SetBitmap(TmpBmp);

	//cleanup 
	if (pOldFont) dc.SelectObject(pOldFont);
	m_Font.DeleteObject();
	dc.Detach();
	free(m_pLF);

	DeleteObject(hbitmap);
	hbitmap=TmpBmp;

	//final cleanup
	SelectObject(TmpDC,TmpObj);
	DeleteDC(TmpDC);
}

m_Placemat is a Bitmap object embedded on the dialog window. It is how I am displaying the bitmap on screen.

I can get the bitmap out, but there does not seem to be any change from the original, no text, no visible difference. I seem to be getting the code wrong somehow. Can anyone enlighten me?

I have already posted on the comments section of the page witht he code, but I was hoping for some opinions from someone fast.

I'm running this using VC 6.0, no GDI+ library. If this truely cannot be done on pre-.Net, please tell me

My final objective is to get a text string into pixels or a bit array. If you have a better solution to achieve this, please let me know too.

Thanks.

enhzflep26-Nov-08 17:26

enhzflep

26-Nov-08 17:26

It's no biggie, really.

I think you'll find the problem to lie in the fatc that you deselect your loaded bitmap from the DC before you draw the text on it.

Here's some plain win32 code that hacks togeter a result.

// draws text on a bitmap
void DrawOnBitmap(HBITMAP hBmp)
{
    HFONT oldFnt, font1;
    HDC memDC;
    HBITMAP oldBM;
    char *myText = "CrackerJack";

    // create a mem dc
    memDC = CreateCompatibleDC(NULL);

    // select bitmap into it
    oldBM = (HBITMAP)SelectObject(memDC, hBmp);

    //create the font
    font1 = CreateFont(-13, 0, 0, 0, 400, FALSE, FALSE, FALSE, 1, 400, 0, 0, 0, "Tahoma Bold");
    oldFnt = (HFONT)SelectObject(memDC, font1);

    // show text at arbitrary position
    TextOut(memDC, 30, 30, myText, strlen(myText));

    // clean-up time!
    SelectObject(memDC, oldBM);
    SelectObject(memDC, oldFnt);
    DeleteObject(font1);
    DeleteDC(memDC);
}

simon

modified on Thursday, November 27, 2008 12:52 AM

JJeffrey26-Nov-08 19:35

26-Nov-08 19:35

Thanks for the quick reply. I appreciate it.

I have put your function as such:

void DrawOnBitmap(HBITMAP hBmp)
{    
    HFONT oldFnt, font1;
    HDC memDC;
    HBITMAP oldBM;    
	// some arbitrary junk text
    char *myText = "Testing";  
	
	// create a mem dc
    memDC = CreateCompatibleDC(NULL);    
	
	// select bitmap into it
    oldBM = (HBITMAP)SelectObject(memDC, hBmp);    

	
	//create the font
    font1 = CreateFont(-13, 0, 0, 0, 400, FALSE, FALSE, FALSE, 1, 400, 0, 0, 0, "Tahoma Bold");
    oldFnt = (HFONT)SelectObject(memDC, font1);        
	
	// print text at an arbitrary position
    TextOut(memDC, 30, 30, myText, strlen(myText));

    m_Placemat.SetBitmap(oldBM);   //Output Bitmap into Dialog Box CStatic object

	// clean-up time!
    SelectObject(memDC, oldBM);
    SelectObject(memDC, oldFnt);
    DeleteObject(oldBM);
    DeleteObject(oldFnt);
    DeleteDC(memDC);
}

void OnTest() 
{
	HBITMAP hbitmap = ::LoadBitmap(AfxGetInstanceHandle(), MAKEINTRESOURCE(IDB_BITMAP3));
        DrawOnBitmap(hbitmap);
}

What I get back is a black BMP.

The point when
oldBM = (HBITMAP)SelectObject(memDC, hBmp);
was executed, the BMP turned entirely black (when i tried to output at that point). I think when the CreateCompatibleDC is executed with a null, there creates a problem. I tried passing in the DC I used previously but it doesn't make a difference.

When I run
m_Placemat.SetBitmap(hBmp);
instead, I get a black box with a smaller grey box in the centre.

I have tried integrating your Font section into mine:

void CCaptureAndDisplayDlg::OnTest() 
{

	HBITMAP hbitmap = ::LoadBitmap(AfxGetInstanceHandle(), MAKEINTRESOURCE(IDB_BITMAP3));

	BITMAP bitm;
	GetObject( hbitmap, sizeof(BITMAP), &bitm );
	long width=bitm.bmWidth;
	long height=bitm.bmHeight;
	BITMAPINFO bmInfo;
	CBitmap	FinalBMP;
	int rtn=0;

	memset(&bmInfo.bmiHeader,0,sizeof(BITMAPINFOHEADER));
	bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
	bmInfo.bmiHeader.biWidth=width;
	bmInfo.bmiHeader.biHeight=height;
	bmInfo.bmiHeader.biPlanes=1;
	bmInfo.bmiHeader.biBitCount=24;

	//create a temporary dc in memory.
	HDC pDC = ::GetDC(0);
	HDC TmpDC=CreateCompatibleDC(pDC);

	//create a new bitmap and select it in the memory dc
	BYTE *pbase;
	HBITMAP TmpBmp=CreateDIBSection(pDC, &bmInfo,DIB_RGB_COLORS,(void**)&pbase,0,0);
	HGDIOBJ TmpObj=SelectObject(TmpDC,TmpBmp);

	//draw the background
	HDC dcBmp=CreateCompatibleDC(TmpDC);
	HGDIOBJ TmpObj2 = SelectObject(dcBmp,hbitmap);
	BitBlt(TmpDC,0,0,width,height,dcBmp,0,0,SRCCOPY);
	SelectObject(TmpDC,TmpObj2);
	DeleteDC(dcBmp);

// Insert Font and Write code here
	char *myText = "Testing"; 
	HFONT oldFnt, font1;
        font1 = CreateFont(-13, 0, 0, 0, 400, FALSE, FALSE, FALSE, 1, 400, 0, 0, 0, "Tahoma Bold");
        oldFnt = (HFONT)SelectObject(TmpDC, font1);        
	
	// print text at an arbitrary position
        TextOut(TmpDC, 330, 230, myText, strlen(myText));

	m_Placemat.SetBitmap(TmpBmp);


        SelectObject(TmpDC, oldFnt);
        DeleteObject(oldFnt);
        DeleteDC(TmpDC);
}

This way I get my BMP displayed, but still no text.

This has to be my understanding of the whole workings of this BMP thing going wonky because i don't know why it doesn't work on my system.

Am I doing this all wrong?

enhzflep26-Nov-08 19:48

enhzflep

26-Nov-08 19:48

Hi there.

Just looking at your implementation of void DrawOnBitmap(HBITMAP hBmp), I notice that you set the bitmap image of the m_Placemat to be the image that _was_ originally selected into the temporary DC - This image has had nothing done to it, so it should be black. Poke tongue | ;-P

Following selecting this empty bitmap, you still do the call to DeleteObject(oldBM)...

I suggest you try changing

m_Placemat.SetBitmap(oldBM);   //Output Bitmap into Dialog Box CStatic object

m_Placemat.SetBitmap(hBmp);   //Output Bitmap into Dialog Box CStatic object

Since you want to display the loaded bitmap with the added text in your program, and not the (since deleted) empty bitmap that belonged to the temporary DC we created.

Please, let me know if I've been unclear/it doesn't work for you.

JJeffrey26-Nov-08 20:52

26-Nov-08 20:52

I've tried that.

Running

m_Placemat.SetBitmap(hBmp);

results in a black image with an grey centre (the grey of a standard Dialog window, so i think it's hollow)

I can output text on a blank window like this:

void CGDITest::OnDraw(CDC* pDC)
{
	CGDITestDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);

	pDC->TextOut(50, 42, "Testing", 13);
}

so I don't think it's my VC 6's SDK, I must be doing something wrong...

Can I use the plain pDC->TextOut to get an array of bits that make up the string? Without trying to write it on a standard white bitmap?

I'm really lost now.

And Thank you again for replying.

enhzflep26-Nov-08 21:04

enhzflep

26-Nov-08 21:04

JJeffrey wrote:
I've tried that.

Oops! Sorry i missed that the first time round.

Hmmmm, I've no idea about pDC->TextOut as I'm away from my other pc.

Something else to consider, are the loaded and created bitmaps of comparable bits/pixel - sorry, it's all i can think of right now.

JJeffrey26-Nov-08 21:37

26-Nov-08 21:37

Thanks for your time. I appreciate it. Maybe I should try from a different angle or something.

I don't see how, personally, the bits/pixel ratio could affect the writing of the text. If I use a smaller resolution picture (less colour palette size), I don't see why text would suddenly be able to be written.

Anyway, thanks. Hope my boss doesn't kill me for not getting this.... :p

Re: Having difficulty writing text on a bitmap [modified]

PJ Arends27-Nov-08 7:13

PJ Arends

27-Nov-08 7:13

Have a look at http://www.codeproject.com/KB/applications/imageviewer.aspx[^]. It is a tool I wrote to help debug graphics problems. It may help you figure this out.

You may be right
I may be crazy
-- Billy Joel --

Within you lies the power for good - Use it!

JJeffrey27-Nov-08 15:49

Cursor not changing [modified]

27-Nov-08 15:49

Thank you, Thank you... THANK. YOU!

Your program is fantastic. I see where it went wrong now, the SelectObjects were causing the HDCs to overwrite with old images as they weren't done properly (I think...). I delayed it till later in the code.

For the record, this code works:

void CCaptureAndDisplayDlg::OnTest() 
{

	HBITMAP hbitmap = ::LoadBitmap(AfxGetInstanceHandle(), MAKEINTRESOURCE(IDB_BITMAP1));

	BITMAP bitm;
	GetObject( hbitmap, sizeof(BITMAP), &bitm );
	long width=bitm.bmWidth;
	long height=bitm.bmHeight;
	BITMAPINFO bmInfo;
	int rtn=0;

	memset(&bmInfo.bmiHeader,0,sizeof(BITMAPINFOHEADER));
	bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
	bmInfo.bmiHeader.biWidth=width;
	bmInfo.bmiHeader.biHeight=height;
	bmInfo.bmiHeader.biPlanes=1;
	bmInfo.bmiHeader.biBitCount=24;

	//create a temporary dc in memory.
	HDC pDC = ::GetDC(0);
	HDC TmpDC=CreateCompatibleDC(pDC);

	//create a new bitmap and select it in the memory dc
	BYTE *pbase;
	HBITMAP TmpBmp=CreateDIBSection(pDC, &bmInfo,DIB_RGB_COLORS,(void**)&pbase,0,0);
	HGDIOBJ TmpObj=SelectObject(TmpDC,TmpBmp);

	//draw the background
	HDC dcBmp=CreateCompatibleDC(TmpDC);
	HGDIOBJ TmpObj2 = SelectObject(dcBmp,hbitmap);

	BitBlt(TmpDC,0,0,width,height,dcBmp,0,0,SRCCOPY);

	char *myText = "Testing"; 
	HFONT oldFnt, font1;
        font1 = CreateFont(-13, 0, 0, 0, 400, FALSE, FALSE, FALSE, 1, 400, 0, 0, 0, "Tahoma Bold");
        oldFnt = (HFONT)SelectObject(TmpDC, font1);        
	
	// print text at an arbitrary position
        TextOut(TmpDC, 30, 30, myText, strlen(myText));

        SelectObject(TmpDC,TmpObj2);
	m_Placemat.SetBitmap(TmpBmp);

        SelectObject(TmpDC, oldFnt);
        DeleteObject(oldFnt);
        DeleteDC(TmpDC);
	DeleteDC(dcBmp);
}

Great Program you have there....

Jeffrey

modified on Friday, November 28, 2008 1:40 AM

Leslie Sanford26-Nov-08 9:00

Leslie Sanford

26-Nov-08 9:00

I've written a custom GUI library for creating GUI's for my VST plugins. I would love to use MFC, but I've never gotten them to play together nicely (long story).

Anyway, the GUI library has come together well, but there are a few anomalies to work out. The one I'm dealing with right now is a problem with the cursor.

In VST, the host asks the plugin to create a child window representing the plugin's UI. It's the host's job to display the window. All of this works well, but what I've noticed is that if I move the cursor from outside my GUI window to inside the window, sometimes the cursor shape doesn't change. For example, it may get stuck with the resizing handle image.

I've noticed that this problem doesn't occur in a standalone app I made with my library. I've made sure when registering the GUI window class that I used the obligatory: ::LoadCursor(instance, IDC_ARROW).

There's way too much code for me to post anything here. So I'm just looking for some general clues.

EDIT: Strange. I changed the code to ::LoadCursor(NULL, IDC_ARROW), and it fixed the problem.

modified on Wednesday, November 26, 2008 3:09 PM

Re: Cursor not changing

CPallini26-Nov-08 9:30

26-Nov-08 9:30

Leslie Sanford wrote:
EDIT: Strange. I changed the code to ::LoadCursor(NULL, IDC_ARROW), and it fixed the problem.

Not so strange if you have a look at documentation [^]:

To use one of the predefined cursors, the application must set the hInstance parameter to NULL

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: Cursor not changing

Leslie Sanford26-Nov-08 10:06

Leslie Sanford

26-Nov-08 10:06

CPallini wrote:
Not so strange if you have a look at documentation

Yup. I should have checked out the documenation. Having worked with the Windows API this long, I should have realized that simply taking a function at face value and passing it what it appears to want is not always the correct thing to do.

Sorry if that sounds like whining. It's just that these special cases, these gotchas, add up over time to a point of making an API hard to use.

Re: Cursor not changing

CPallini26-Nov-08 10:17

<tag>/, source code questions</tag>

26-Nov-08 10:17

Reading the documentation is the best way to avoid headaches, when dealing with Windows API. Big Grin | :-D

ForNow26-Nov-08 6:26

ForNow

26-Nov-08 6:26

Hi,

seems like i just got aome people angry at me by not posting code the right way in the message

Just read up on the tag/pretag so......

My question is do I have to put a start tag / end tag on every line of code that

I post ?????? in addtion when I tag my code do I have to check the ignore HTML box or

not

thankx and sorry

Maximilien26-Nov-08 6:52

Maximilien

26-Nov-08 6:52

put your code between pre tags.

/// some coed

jeron126-Nov-08 7:16

jeron1

26-Nov-08 7:16

Maximilien wrote:
/// some coed

Got something else on your mind? Big Grin | :-D

CPallini26-Nov-08 7:13

26-Nov-08 7:13

You should use the code block button or, manually, the <pre> tags, this way:

<code><pre></code>
// code snippet here
<code></pre></code>

led mike26-Nov-08 7:21

led mike

26-Nov-08 7:21

ForNow wrote:
seems like i just got aome people angry

Angry? We may have had some fun with you but I didn't see anyone getting angry. Did I miss something?

led mike

CPallini26-Nov-08 7:46