directshow 之 视频位图24位32位存储

HRESULT CVideoSource::SaveToBmpFile(char* szFile)
{
HRESULT hr =NULL;

TRY
{
BYTE *buffer = NULL;
hr = m_pWindowsLessControl->GetCurrentImage(&buffer);
if (!SUCCEEDED(hr))
{
return hr;
}

BITMAPFILEHEADER hdr;
BITMAPINFOHEADER *lpbi = (BITMAPINFOHEADER *)buffer;
//颜色空间转换，如果为32位位图，转换为24
bool isSize24 = false;
DWORD dwSize24 = 0;
DWORD dwSize32 = lpbi->biSizeImage;
dwSize24 = lpbi->biBitCount==32?(dwSize32*3)/4:dwSize32; //RGB32与RGB24的像素点空间只差了一个字节
BYTE* pImg24 = new BYTE[dwSize24]; //存放RGB24存储空间
BYTE* pImg24Temp = pImg24;
BYTE* pImg32 = buffer + sizeof(BITMAPINFOHEADER);
if (lpbi->biBitCount==32)
{
isSize24 = true;
for (DWORD index=0; index<dwSize32/4; index++)
{
unsigned char r = *(pImg32++);
unsigned char g = *(pImg32++);
unsigned char b = *(pImg32++);
pImg32++; //跳过alpha分量，实现转换
*(pImg24++) = r;
*(pImg24++) = g;
*(pImg24++) = b; //赋值
}

lpbi->biBitCount = 24;
}
int nColors = 1 << lpbi->biBitCount;
if (nColors > 256)
nColors = 0;
hdr.bfType = ((WORD)('M' << 8) | 'B'); // always is "BM"
hdr.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + nColors * sizeof(RGBQUAD) + lpbi->biSizeImage;
hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;
hdr.bfOffBits = (DWORD)(sizeof(BITMAPFILEHEADER) + lpbi->biSize + nColors * sizeof(RGBQUAD));

//将图像调整为640*480,非这种格式，强制调整

FILE *bmpFile = NULL;
bmpFile = fopen((LPCTSTR)szFile, "wb");//inFile为文件名
if (bmpFile != NULL)
{
fwrite(&hdr, 1, sizeof(BITMAPFILEHEADER), bmpFile);//位图文件头
fwrite(buffer, 1, sizeof(BITMAPINFOHEADER), bmpFile);//位图信息头
if (!isSize24)
{
fwrite(buffer+sizeof(BITMAPINFOHEADER), 1, nColors * sizeof(RGBQUAD), bmpFile);//颜色表
fwrite(buffer+sizeof(BITMAPINFOHEADER)+nColors * sizeof(RGBQUAD), 1, lpbi->biSizeImage, bmpFile);//位图数据
}
else
{
fwrite(pImg24Temp,1,dwSize24,bmpFile);
//fwrite(pImgNormal,1,700*500*3,bmpFile);
}
}
fclose(bmpFile);

CoTaskMemFree(buffer);//释放资源
delete pImg24Temp;
return hr;
}
CATCH (CMemoryException, e)
{

}
END_CATCH
}