Re: stretchdibits fails

From:

Roland <ajay.sonawane@gmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 02 Aug 2007 07:15:25 -0700

Message-ID:

<1186064125.530973.244970@x35g2000prf.googlegroups.com>

Hi Joseph,

I will tell you what I wanted to achieve here. I want to convert AVI
having resolution cxscreen *cyscreen to 320*240. I already have
classes and functions that does screen recording and saves AVI file. I
am using BitBlt to copy screen bitmap to DC while screen capture and
at end of recording I save the video file. My program will always
capture full dekstop but need to change the resolution of resultant
AVI.Thats why I came up with a solution to use StretchBlt to 320*240
and some changes while AVI Initialization. I used SetStretchBltMode
with parameter HALFTONE. but HALFTONE makes my program very slow and
mouse moves very slowly while recording, So I rejected the idea and
came up with another solution which involves converting full screen
video file to 320*240 after recording.
The below function will parse video file, extract each and every frame
and use strectblt (currently I am just testing it with BitBlt) , Using
SetStrecthBltMode with HALFTONE gives good quality but performs heavy
operation. So I will convert video file after recording thats why it
won't slow my program because at that time I will simply popup one
wait dialog while conversion is in progress, The below function does
the partial job of parsing and converting bitmaps from frames. Now
please tell me Am I on right track ? Am I doing right thing ? After
converting the bitmap I will get hBitmap that I will pass to my
function that will again make an AVI stream.
Could you please correct my code or explain with some good sample
code ?

Thanks a lot !

-Ajay

On Aug 2, 6:48 pm, Joseph M. Newcomer <newco...@flounder.com> wrote:

On Thu, 02 Aug 2007 05:12:56 -0700, Roland <ajay.sonaw...@gmail.com> wrote:

This is my function that I wrote to extract AVI frames from AVI file.
Actually I wanted to get avi frames into DIB format, converter it DDB
and then save it to a file, This is a function that I write to do so,
Here SetDIBits function returns O (Error), I don't know what am I
doing wrong, Could anyone please tell where I am wrong.

BOOL CAviFile::ExtractAVIFrames(CString szFileName)
{
   AVIFileInit();

   PAVIFILE avi;
   int res = AVIFileOpen(&avi, szFileName, OF_READ, NULL);

   if (res!=AVIERR_OK)
   {
       //an error occures
       if (avi != NULL)
           AVIFileRelease(avi);

       return FALSE;
   }

   AVIFILEINFO avi_info;
   AVIFileInfo(avi, &avi_info, sizeof(AVIFILEINFO));

   CString szFileInfo;
   szFileInfo.Format(_T("Dimention: %dx%d\n")
                     _T("Length: %d frames\n")
                     _T("Max bytes per second: %d\n")
                     _T("Samples per second: %d\n")
                     _T("Streams: %d\n")
                     _T("File Type: %d"), avi_info.dwWidth,
                           avi_info.dwHeight,
                           avi_info.dwLength,
                           avi_info.dwMaxBytesPerSec,
                           (DWORD) (avi_info.dwRate /
avi_info.dwScale),
                           avi_info.dwStreams,
                           avi_info.szFileType);

   //AfxMessageBox(szFileInfo, MB_ICONINFORMATION | MB_OK);

   PAVISTREAM pStream;
   res=AVIFileGetStream(avi, &pStream, streamtypeVIDEO /*video
stream*/,
                                              0 /*first stream*/);

   if (res!=AVIERR_OK)
   {
       if (pStream!=NULL)
           AVIStreamRelease(pStream);

       AVIFileExit();
       return FALSE;
   }

   //do some task with the stream
   int iNumFrames;
   int iFirstFrame;

   iFirstFrame=AVIStreamStart(pStream);
   if (iFirstFrame==-1)
   {
       //Error getteing the frame inside the stream

       if (pStream!=NULL)
           AVIStreamRelease(pStream);

       AVIFileExit();
       return FALSE;
   }

   iNumFrames=AVIStreamLength(pStream);
   if (iNumFrames==-1)
   {
       //Error getteing the number of frames inside the stream

       if (pStream!=NULL)
           AVIStreamRelease(pStream);

       AVIFileExit();
       return FALSE;
   }

   PGETFRAME pFrame;
   pFrame = AVIStreamGetFrameOpen(pStream,NULL/*(BITMAPINFOHEADER*)
AVIGETFRAMEF_BESTDISPLAYFMT*/ /*&bih*/);

   //Get the first frame
   int index=0;

       for (int i = iFirstFrame; i<iNumFrames; i++)
   {
               HBITMAP hBitmap;

       index = i-iFirstFrame;

               BYTE* pDIB = (BYTE*) AVIStreamGetFrame(pFrame, index);
               if(!pDIB)
               {
                       TCHAR szError[1024]={0};
                       wsprintf(szError,_T("AVIStreamGetFrame failed
to return DIB bits,
Error:%d"),GetLastError());
                       OutputDebugString(szError);

****
Have you considered using the TRACE macro?
****> }

int iHeight = ((LPBITMAPINFOHEADER)pDIB)->biHeight;
int iWidth = ((LPBITMAPINFOHEADER)pDIB)->biWidth;

****
What values are you seeing here? Also, given that the actual value is a BITMAPINFO
structure, it would have struck me that the correct casting would have been
int iHeight = ((LPBITMAPINFO)pDIB)->bmiHeader.biHeight
because a BITMAPINFO structure also has a RGBQUAD value, which is actually a
variable-length structure and should be accounted for.
****

               HDC hDC = GetDC(NULL);
               if(!hDC)
               {
                       TCHAR szError[1024]={0};
                       wsprintf(szError,_T("CreateCompatibleDC
failed, Error:
%d"),GetLastError());
                       OutputDebugString(szError);
               }

               // Get compatible DC
               HDC hMemDC = CreateCompatibleDC(hDC);
               if(!hMemDC)
               {
                       TCHAR szError[1024]={0};
                       wsprintf(szError,_T("CreateCompatibleDC
failed, Error:
%d"),GetLastError());
                       OutputDebugString(szError);
               }

               hBitmap =
CreateCompatibleBitmap(hMemDC,iWidth,iHeight);
               if(!hBitmap)
               {
                       TCHAR szError[1024]={0};
                       wsprintf(szError,_T("CreateCompatibleBitmap
failed, Error:
%d"),GetLastError());
                       OutputDebugString(szError);
               }

               BITMAPINFO bmpInfo;

               ZeroMemory(&bmpInfo,sizeof(bmpInfo));
               bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
               bmpInfo.bmiHeader.biBitCount = 32;
               bmpInfo.bmiHeader.biCompression = BI_RGB;
               bmpInfo.bmiHeader.biSizeImage = iWidth * iHeight * 4;
               bmpInfo.bmiHeader.biPlanes = 1;
               bmpInfo.bmiHeader.biHeight = iHeight;
               bmpInfo.bmiHeader.biWidth = iWidth;

               //get the BitmapInfoHeader
               BITMAPINFOHEADER bih;
               RtlMoveMemory(&bih.biSize, pDIB,
sizeof(BITMAPINFOHEADER));

***
Why are you doing a copy? Why not do
LPBITMAPHADER = (LPBITMAPHEADER)pDIB);

Note there is a serious error here, since you seem to have mistaken a BITMAPINFOHEADER for
the specified BITMAPHEADER
****

               //now get the bitmap bits
               if (bih.biSize < 1)
               {
                       return FALSE;
               }

               BYTE* Bits = new BYTE[bih.biSize];
               RtlMoveMemory(Bits, pDIB + sizeof(BITMAPINFOHEADER),
bih.biSize);

****
I'm curious why you are allocating new memory and doing something like RtlMoveMemory when
you could just have used pDIB as the input parameter. Also, see my above observation
about the fact that the structure is a BITMAPINFO, not a BITMAPINFOHEADER, and therefore
appears to have at least one RGBQUAD value present, where in this case you are copying the
wrong bits. I would suggest that copying the bits is an error, and getting the address of
the bits is probably the best approach. But make sure it is the *correct* address

From the MSDN:

"A DIB consists of two distinct parts: a BITMAPINFO structure describing the dimensions
and colors of the bitmap, and an array of bytes defining the pixels of the bitmap. The
bits in the array are packed together, but each scan line must be padded with zeroes to
end on a LONG data-type boundary. If the height of the bitmap is positive, the bitmap is a
bottom-up DIB and its origin is the lower-left corner. If the height is negative, the
bitmap is a top-down DIB and its origin is the upper left corner.

A bitmap is packed when the bitmap array immediately follows the BITMAPINFO header. Packed
bitmaps are referenced by a single pointer. For packed bitmaps, the biClrUsed member must
be set to an even number when using the DIB_PAL_COLORS mode so that the DIB bitmap array
starts on a DWORD boundary. "

It does *not* say "...a BITMAPINFOHEADER structure immediately followed by an array of
bytes..."

BYTE memBitmapInfo[40];

****
How did you get the strange value "40" as being valid? I don't think so. Perhaps
sizeof(BITMAPINFO) would work here, but 40? Really? How could you have ANY idea that the
size of this structure is 40? (It might be in some release of the Platform SDK, but there
is no reason to assume this is actually always true, and in any case, there is no reason
to allocate this and make a copy!)
****> RtlMoveMemory(memBitmapInfo, &bih, sizeof(bih));

****
But why are you doing yet another unnecessary copy operation?
        int nScanLines = ::SetDIBits(hDC, hBitmap,
                        0, abs(iHeight),
                        Bits, bih, DIB_RGB_COLORS);

Note that to make this work, I did not make two copies of the header, but just set
LPBITMAPINFO bih = (LPBITMAPINFO)pDIB. Note that iHeight is the number of scan lines. But
read that statement about positive and negative values. iHeight could be negative, but
then it is not a count of scan lines. And Bits would not be a buffer into which a copy
was made, it would be just a pointer to the buffer that is already present.

This would probably have been obvious had you actually printed these values out. With all
the stuff you are printing, why didn't you consider printing out the parameters to your
call?
****

               int nScanLines = SetDIBits(hDC, hBitmap, 0, iHeight,
Bits,
(BITMAPINFO*)memBitmapInfo, DIB_RGB_COLORS);

               TCHAR szError[1024]={0};
               wsprintf(szError,_T("SetDIBits, No Of scan lines:%d,
Error:
%d"),nScanLines,GetLastError());
               OutputDebugString(szError);

               // Create DDB into hMemDC
               HBITMAP hOldBitmap = (HBITMAP)SelectObject(hDC,
hBitmap);

               // Copy hMemDC into hDC
               if(!BitBlt(hMemDC, 0, 0, (WORD)iWidth,
(WORD)iHeight,hDC,0, 0,
SRCCOPY))

****
Why a WORD cast? The BitBlt documentation *clearly* states that these values are int
values! This code is potentially erroneous because it is forcing a completely
inappropriate cast
****> {

TCHAR szError[1024]={0};

****
Why is this being initialized when you are about to overwrite it?
****> wsprintf(szError,_T("BitBlt failed , Error:

%d"),GetLastError());

****
wsprintf is one of those functions whose existence you should forget about. It is
considered dangerous. Use either strsafe.h and use StringCchPrintf or in VS2005 use
wsprintf_s. Better still, use the TRACE macro
****> OutputDebugString(szError);

               }

               hBitmap = (HBITMAP) SelectObject(hMemDC, hOldBitmap);

               SaveBitmap("C:\\Capture.bmp",hBitmap);

****
I truly hope this is not a real example from your code. Assuming the C: drive exists, and
assuming that you can create files in it, are invalid assumptions.
****

delete [] Bits;

****
Since there was no purpose in copying them, there is no purpose in deleting them.
****

               DeleteObject(SelectObject(hMemDC, hBitmap));
               DeleteDC(hMemDC);
               ReleaseDC(NULL,hDC);
               //CreateFromPackedDIBPointer(pDIB, index);
   }

   AVIStreamGetFrameClose(pFrame);

   //close the stream after finishing the task
   if (pStream!=NULL)
       AVIStreamRelease(pStream);

   AVIFileExit();

   return TRUE;

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