write XImage to .bmp file in C

问题

I am writing an XImage to a file "bitmap0.bmp" using the following code but when i open the newly created file with imageViewer in fedora it gives "Premature end of file" error and does not display anything. could anyone please point out the problem in the following code?

typedef struct tagBITMAPFILEHEADER {
WORD    bfType;
DWORD   bfSize;
WORD    bfReserved1;
WORD    bfReserved2;
DWORD   bfOffBits;

} BITMAPFILEHEADER;

typedef struct tagBITMAPINFOHEADER{
DWORD  biSize;
LONG   biWidth;
LONG   biHeight;
WORD   biPlanes;
WORD   biBitCount;
DWORD  biCompression;
DWORD  biSizeImage;
LONG   biXPelsPerMeter;
LONG   biYPelsPerMeter;
DWORD  biClrUsed;
DWORD  biClrImportant;

} BITMAPINFOHEADER;

void saveXImageToBitmap(XImage *pImage)
{
BITMAPFILEHEADER bmpFileHeader;
BITMAPINFOHEADER bmpInfoHeader;
FILE *fp;
static int cnt = 0;
int dummy;
char filePath[255];
memset(&bmpFileHeader, 0, sizeof(BITMAPFILEHEADER));
memset(&bmpInfoHeader, 0, sizeof(BITMAPINFOHEADER));
bmpFileHeader.bfType = 0x4D42;
bmpFileHeader.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) +  pImage->width*pImage->height*4;
bmpFileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
bmpFileHeader.bfReserved1 = 0;
bmpFileHeader.bfReserved2 = 0;

bmpInfoHeader.biSize = sizeof(BITMAPINFOHEADER);
bmpInfoHeader.biWidth = pImage->width;
bmpInfoHeader.biHeight = pImage->height;
bmpInfoHeader.biPlanes = 1;
bmpInfoHeader.biBitCount = 32;
dummy = (pImage->width * 3) % 4;
if((4-dummy)==4)
    dummy=0;
else
    dummy=4-dummy;
bmpInfoHeader.biSizeImage = ((pImage->width*3)+dummy)*pImage->height;
bmpInfoHeader.biCompression = 0;
bmpInfoHeader.biXPelsPerMeter = 0;
bmpInfoHeader.biYPelsPerMeter = 0;
bmpInfoHeader.biClrUsed = 0;
bmpInfoHeader.biClrImportant = 0;

sprintf(filePath, "bitmap%d.bmp", cnt++);
fp = fopen(filePath,"wb");

if(fp == NULL)
    return;

fwrite(&bmpFileHeader, sizeof(bmpFileHeader), 1, fp);
fwrite(&bmpInfoHeader, sizeof(bmpInfoHeader), 1, fp);
fwrite(pImage->data, 4*pImage->width*pImage->height, 1, fp);
fclose(fp);

}