Solved

Hbitmap to RGB Buffer help

Posted on 2014-02-22
7
853 Views
Last Modified: 2014-02-26
Hello,

inside an external DLL I have a function to set a RGB Buffer for a logo to render. This function is:
 void       SetLogo(unsigned char *RGBBuf, int width, int strideLen, int height); // sets the actual logo 

Open in new window


The description of this function is:
RGBBuf is a bitmap buffer, which contains a large bitmap width * height. Because Windows bitmaps still have padding inside, one must also specify strideLen in bytes, that is the line size. Without padding the line size is width * 3, with padding it varies between width * 3 + 0 and width * 3 + 3

I use now following code:
void CDVDConverterWork::GetImageForLogo()
{
	HBITMAP hBitmap = (HBITMAP)LoadImage(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_OVLLOGO), IMAGE_BITMAP, 0, 0, 0); 

	BITMAP bm;
	::GetObject( hBitmap , sizeof(bm) , &bm );

	/* Omitting error checks for brevity */
	HDC dcBitmap = CreateCompatibleDC ( NULL );
	SelectObject( dcBitmap, hBitmap );

	BITMAPINFO bmpInfo;
	bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmpInfo.bmiHeader.biWidth = bm.bmWidth;
	bmpInfo.bmiHeader.biHeight = -bm.bmHeight;
	bmpInfo.bmiHeader.biPlanes = 1;
	bmpInfo.bmiHeader.biBitCount = 24;
	bmpInfo.bmiHeader.biCompression = BI_RGB;        
	bmpInfo.bmiHeader.biSizeImage = 0;  

	 
	unsigned char* retArray = new unsigned char[bmpInfo.bmiHeader.biSizeImage];

	//LPVOID retArray = malloc(bmpInfo.bmiHeader.biSizeImage);
	GetDIBits( dcBitmap , hBitmap , 0 , bm.bmHeight , retArray , &bmpInfo , DIB_RGB_COLORS );

	
	m_pConverter->SetLogo(retArray,bm.bmWidth, bmpInfo.bmiHeader.biSizeImage, bm.bmHeight);
	m_pConverter->EnableLogo(true);
	
}

Open in new window


But I get now crashes inside the DLL. It seems that my function submit wrong data to the DLL.  Any idea what is wrong there?
0
Comment
Question by:Ingo Foerster
  • 2
  • 2
  • 2
  • +1
7 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 39879446
>>Any idea what is wrong there?

You're  allocating an array of size 0:
bmpInfo.bmiHeader.biSizeImage = 0;  

unsigned char* retArray = new unsigned char[bmpInfo.bmiHeader.biSizeImage];

Open in new window


That can't work.
0
 
LVL 10

Expert Comment

by:Korbus
ID: 39879594
Agree with jkr-  perhaps you meant to use: bmpInfo.bmiHeader.biSize  in your new statement?
0
 

Author Comment

by:Ingo Foerster
ID: 39879998
Hi,,
ok, I changed the code:
	HBITMAP hBitmap = (HBITMAP)LoadImage(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_OVLLOGO), IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION | LR_SHARED); 

	BITMAP bm;
	::GetObject( hBitmap , sizeof(bm) , &bm );

	CDC mem_dc;  
	mem_dc.CreateCompatibleDC(NULL);

	/* Omitting error checks for brevity */
	BITMAPINFO bmpInfo;
	bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmpInfo.bmiHeader.biWidth = bm.bmWidth;
	bmpInfo.bmiHeader.biHeight = bm.bmHeight;
	bmpInfo.bmiHeader.biPlanes = bm.bmPlanes;
	bmpInfo.bmiHeader.biBitCount = bm.bmBitsPixel;
	bmpInfo.bmiHeader.biCompression = BI_RGB;        
	bmpInfo.bmiHeader.biSizeImage = 0;  
	bmpInfo.bmiHeader.biClrImportant = 0;
	bmpInfo.bmiHeader.biClrUsed = 0;

	unsigned char *Pixels = (unsigned char *)malloc(bm.bmWidth * bm.bmHeight * 4); //sizeof(unsigned char)

	::GetDIBits(mem_dc.m_hDC, hBitmap, 0, bm.bmHeight, Pixels, &bmpInfo, DIB_RGB_COLORS);
	//GetDIBits( hDC , hBitmap , 0 , bm.bmHeight , Pixels , &bmpInfo , DIB_RGB_COLORS );

	::DeleteObject(hBitmap);
	
	SetLogo(Pixels, bm.bmWidth, bm.bmWidth*3, bm.bmHeight);

Open in new window


But now I have a gray image that is mirrored and is slanted. Any idea what is wrong with my buffer?
0
Free Trending Threat Insights Every Day

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

 
LVL 86

Accepted Solution

by:
jkr earned 500 total points
ID: 39880854
Does the bitmap you are using have padding or not? Multiplying by three seems a bit weird to me. How does it look if you leave out that multiplication?
0
 
LVL 10

Expert Comment

by:Korbus
ID: 39883137
Not sure, but I suspect the params to the LoadImage function:

try LR_VGACOLOR:  "Uses true VGA colors."
rather than LR_CREATEDIBSECTION  : "When the uType parameter specifies IMAGE_BITMAP, causes the function to return a DIB section bitmap rather than a compatible bitmap."

(from : http://msdn.microsoft.com/en-us/library/windows/desktop/ms648045(v=vs.85).aspx)
0
 

Author Closing Comment

by:Ingo Foerster
ID: 39887405
Was the passing issue. Thanks.
0
 
LVL 32

Expert Comment

by:sarabande
ID: 39888109
unsigned char *Pixels = (unsigned char *)malloc(bm.bmWidth * bm.bmHeight * 4);

Open in new window

instead of multiplying times 4 you better should use (bm.bmBitsPixel/8) and instead of a separate pointer Pixels you better have used the bmiColors member array of structure BITMAPINFO.

in case of BI_RGB you have 32 bits per pixel what is 4 bytes what is the size of a RGBQUAD what is 3 bytes for red, green, blue + 1 byte reserved which could be used for specials like alpha blending. an RGBQUAD which has size of int on most systems is more handy than a RGBTRIPLE and the 4th byte could be well used for additional purposes.

nevertheless, when working with bitmaps you never should rely on assumptions but use the information given in the appropriate structures, here in the Bitmap structure.

The BITMAPINFO should have dynamic size such that the bmiColors array has appropriate size:

size_t sizePixels = 0;
BITMAPINFO * pBmpInfo = NULL;
...
sizePixels = bm.bmWidth * bm.bmHeight * (bm.bmBitsPixel/8);
// the structure was created with a size such that the 
// bmiColors member could take the required colors per pixel.
pBmpInfo = (unsigned char *)malloc( (sizeof(BITMAPINFOHEADER) + sizePixels);

pBmpInfo->bmiHeader.biWidth = bm.bmWidth;
pBmpInfo->bmiHeader.biHeight = bm.bmHeight;
...
::GetDIBits(mem_dc.m_hDC, hBitmap, 0, bm.bmHeight, pBmpInfo->bmiColors, &bmpInfo, DIB_RGB_COLORS);

Open in new window


btw, you seem to use the c++ compiler and not the c compiler. if so, you should use new/delete rather than malloc/free.

Sara
0

Featured Post

Enabling OSINT in Activity Based Intelligence

Activity based intelligence (ABI) requires access to all available sources of data. Recorded Future allows analysts to observe structured data on the open, deep, and dark web.

Join & Write a Comment

An Outlet in Cocoa is a persistent reference to a GUI control; it connects a property (a variable) to a control.  For example, it is common to create an Outlet for the text field GUI control and change the text that appears in this field via that Ou…
Windows programmers of the C/C++ variety, how many of you realise that since Window 9x Microsoft has been lying to you about what constitutes Unicode (http://en.wikipedia.org/wiki/Unicode)? They will have you believe that Unicode requires you to use…
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

758 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

17 Experts available now in Live!

Get 1:1 Help Now