C Win32: save .bmp image from HBITMAP

Question

I am working with a framegrabber and need to get the images from computer memory and save them on an image file. after trying for couple of days I end up with the following 2 fu

Answer 1

FORMAT_INFO sFormat;
mvfg_getparam( MVFGPAR_DATAFORMAT, &sFormat, giCurrentGrabberID);
long lFrameSize     = sFormat.lFrameSize;

BYTE *pBitmap = (BYTE*)malloc(FrameSize);
memcpy( pBitmap, CamGetPicture(), FrameSize );
writeBitmapToFile(pBitmap, FrameSize, "tmp.bmp");

/*
 * write our raw data into a bitmap file
 * adding the correct header and put it all
 * together in a single file
 */
int
writeBitmapToFile(void *data, unsigned long size, const char *filename)
{
    bmpFileHeader_t header;
    bmpInfoHeader_t info;
    bmpRGBQuad_t rgb = { 0, 0, 0, 0};
    FILE *out;
    size_t len;
    int i;


    header.type = 0x4d42; // magic sequence 'BM'
    header.size = 0;
    header.res0 = 0;
    header.res1 = 0;
    /* 256 different colors, each is defined by an bmpRBQuad type */
    header.offset = 256 * sizeof(bmpRGBQuad_t) + 
                    sizeof(bmpInfoHeader_t) + sizeof(bmpFileHeader_t);
    info.size = sizeof(bmpInfoHeader_t);
    info.width = WIDTH;
    info.height = HEIGHT;
    info.planes = 1;
    info.cDepth = 8; /* 8 Bit */
    info.compression = 0;
    info.rawSize = size;
    info.hRes = 0;
    info.vRes = 0;
    info.nrColors = 0x100;
    info.impColors = 0;

    out = fopen(filename, "wb");
    if (out == NULL) {
        printf("error cannot open %s for writing\n", filename);
        return -1;
    }
    len = fwrite(&header, 1, sizeof(header), out);
    if (len != sizeof(header)) {
        printf("error while writing header\n");
        return -1;
    }
    len = fwrite(&info, 1, sizeof(info), out);
    if (len != sizeof(info)) {
        printf("error while writing info header\n");
        return -1;
    }
    /* stupid try and error programming leads to this */
    for (i = 0; i < 256; i++) {
        rgb.red = i;
        rgb.green = i;
        rgb.blue = i;
        len = fwrite(&rgb, 1, sizeof(rgb), out);
        if (len != sizeof(rgb)) {
            printf("error while writing rgb header\n");
            return -1;
        }
    }

    len = fwrite(data, 1, size, out);
    if (len != size ) {
        printf("error while writing bitmap data\n");
        return -1;
    }
    return 0;
}

Reference - mikrotron

Reference - write bitmap

Answer 2

I just find out I had a silly mistake in another part of my code I was using :

// Convert Image to bitmap and display it
DrawPicture( ghDCMain, pWinGBitmap, gpbImageData, lXSize, lYSize  );    
if(counter!=1) {
  hBitmap2 = CreateCompatibleBitmap (hDCBits, lXSize, lYSize);
  SaveToFile(hBitmap2, "c:\\t.bmp");
  OutputDebugString("tested !!!!");
}

by deleting the hBitmap2 = CreateCompatibleBitmap (hDCBits, lXSize, lYSize); line, and changing the hBitmap2 to hBitmap the result of CreateDIBSection(), it saved the image beautifully. THANK YOU EVERYONE FOR YOUR HELP.

Answer 3

From the documentation for CreateCompatibleDC:

When the memory DC is created, its display surface is exactly one monochrome pixel wide and one monochrome pixel high. Before an application can use a memory DC for drawing operations, it must select a bitmap of the correct width and height into the DC.

Since you're using CreateDIBSection with that DC, the resulting DIB section will be 1-bit monochrome as well.

Answer 4

Are you sure there is proper data in there?

I would try extract the RGB data and save it in some very simple format "manually", just to see what is in there. If you are looking for a dead simple but still standard image format, look at PPM images.