Use the GetPixelFormat and DescribePixelFormat functions to examine a device context's current pixel format, as shown in the following code fragment:
PIXELFORMATDESCRIPTOR pfd;
HDC hdc;
int iPixelFormat;
// if the device context has a current pixel format ...
if (iPixelFormat = GetPixelFormat(hdc)) {
// obtain a detailed description of that pixel format
DescribePixelFormat(hdc, iPixelFormat,
sizeof(PIXELFORMATDESCRIPTOR), &pfd);
}