用Directshow来开发摄像头程序，怎么设置亮度，对比度等参数

[wzckr]

摄像头已经可以用了，不过我想要在程序里加上亮度，对比等参数的设置，在网上找到的代码是这样的
C#代码是这样的
private void SetBrightness(IBaseFilter capFilter, int iBrightness)
{
IAMVideoProcAmp videoProcAmp = capFilter as IAMVideoProcAmp;
int Val;
DirectShowLib.VideoProcAmpFlags Flags = VideoProcAmpFlags.Auto;
videoProcAmp.Get(VideoProcAmpProperty.Brightness, out Val, out Flags);
if (m_brightness != 0)
{
videoProcAmp.Set(VideoProcAmpProperty.Brightness, m_brightness, Flags);
}
else
{
...
}
}

IAMVideoProcAmp videoProcAmp = capFilter as IAMVideoProcAmp;这一句我想改成vb.net 应该是
dim videoProcAmp as IAMVideoProcAmp 可是后面这一部分我就看不懂了，不知道要怎么办
这个接口要怎么写，请高手帮助，最好是有完整一点的代码，可是让我看清楚一点

[keepfool]

在DirectShow，对很多设置可以通过 IAMVideoProcAmp接口设置亮度、对比度等属性

下面m_pVideo是源设备Filter，

   IAMVideoProcAmp *pProcAmp = 0;
   hr = m_pVideo->QueryInterface(IID_IAMVideoProcAmp, (void**)&pProcAmp);
   if(SUCCEEDED(hr))
   {
    long Min, Max, Step, Default, Flags, Val;

    // 亮度. 
    if( g_Brightness > 0 )
    {
     hr = pProcAmp->GetRange(VideoProcAmp_Brightness, &Min, &Max, &Step,
      &Default, &Flags);
     if(SUCCEEDED(hr))
     {
      hr = pProcAmp->Get(VideoProcAmp_Brightness, &Val, &Flags);
      Val = Min+(Max-Min)*g_Brightness/100;
      pProcAmp->Set(VideoProcAmp_Brightness, Val, Flags);
     }
    }

   //对比度
    if( g_Contrast > 0 )
    {
     hr = pProcAmp->GetRange(VideoProcAmp_Contrast, &Min, &Max, &Step,
      &Default, &Flags);
     if(SUCCEEDED(hr))
     {
      hr = pProcAmp->Get(VideoProcAmp_Contrast, &Val, &Flags);
      Val = Min+(Max-Min)*g_Contrast/100;
      pProcAmp->Set(VideoProcAmp_Contrast, Val, Flags);
     }
    }

   //饱和度
    if( g_Saturation > 0 )
    {
     hr = pProcAmp->GetRange(VideoProcAmp_Saturation, &Min, &Max, &Step,
      &Default, &Flags);
     if(SUCCEEDED(hr))
     {
      hr = pProcAmp->Get(VideoProcAmp_Saturation, &Val, &Flags);
      Val = Min+(Max-Min)*g_Saturation/100;
      pProcAmp->Set(VideoProcAmp_Saturation, Val, Flags);
     }
    }
   }

[y1053715398]

请问g_Brightness g_Contrast  这几个变量是怎么来的？