cvShowImage for displaying directly to any window (Feature #1607)

Hi everybody here,
I was developing one DLL involving in image processing for some Win32 applications. It was quite hard trying to display my images directly to a desired window or control. And I found a lot of people having the same troubles. Finally I decided to investigate a little bit through de Highgui code, and decided to write a modification for cvShowImage based on the basic one, but passing to the function the HWND handler of the control you want to display your images rescaled. If it's for your interest, here is the code:

 1CV_IMPL void cvShowImage2( HWND w_hWnd, const CvArr* arr )
 2{
 3    CV_FUNCNAME( "cvShowImage2" );
 4
 5    __BEGIN__;
 6
 7    SIZE size = { 0, 0 };
 8    int channels = 0;
 9    void* dst_ptr = 0;
10    const int channels0 = 3;
11    int origin = 0;
12    CvMat stub, dst, *image;
13    bool changed_size = false;
14    BITMAPINFO* tempbinfo = NULL;
15    HDC hdc = NULL;
16
17    // Ensure we have valid image & HWND
18    if( !arr )
19        return;
20    if( !w_hWnd )
21        return;
22
23    hdc = ::GetDC(w_hWnd);
24
25    if( CV_IS_IMAGE_HDR( arr ))
26        origin = ((IplImage*)arr)->origin;
27
28    CV_CALL( image = cvGetMat( arr, &stub ));
29
30    if ( hdc )
31    {
32        //GetBitmapData
33        BITMAP bmp;
34        GdiFlush();
35        HGDIOBJ h = GetCurrentObject( hdc, OBJ_BITMAP );
36
37        if (h == NULL)
38            return;
39        if (GetObject(h, sizeof(bmp), &bmp) == 0) //GetObject(): returns size of object, 0 if error 
40            return;
41
42        channels = bmp.bmBitsPixel/8;
43        dst_ptr = bmp.bmBits;
44    }
45
46    if( size.cx != image->width || size.cy != image->height || channels != channels0)
47    {
48        changed_size = true;
49
50        uchar buffer[sizeof(BITMAPINFO) + 255*sizeof(RGBQUAD)];
51        BITMAPINFO* binfo = (BITMAPINFO*)buffer;
52
53        BOOL bDeleteObj = DeleteObject(GetCurrentObject( hdc, OBJ_BITMAP));
54        assert( FALSE != bDeleteObj );
55
56        size.cx = image->width;
57        size.cy = image->height;
58        channels = channels0;
59
60        FillBitmapInfo( binfo, size.cx, size.cy, channels*8, 1 );
61        tempbinfo = binfo;
62
63        HGDIOBJ tempImage = SelectObject( hdc, CreateDIBSection( hdc, binfo, DIB_RGB_COLORS, &dst_ptr, 0, 0));
64    } 
65
66    cvInitMatHeader( &dst, size.cy, size.cx, CV_8UC3,dst_ptr, ( size.cx * channels + 3 ) & -4 );
67    cvConvertImage( image, &dst, origin == 0 ? CV_CVTIMG_FLIP : 0 );
68
69    // Image stretching to fit the window
70    RECT rect;
71    GetClientRect(w_hWnd, &rect);
72    int bSuccess = StretchDIBits( hdc,0, 0, rect.right, rect.bottom, 0, 0, image->width, image->height,
73                    dst_ptr, tempbinfo, DIB_RGB_COLORS, SRCCOPY );
74
75    InvalidateRect(w_hWnd, 0, 0);
76
77    __END__;
78}