注意其中的PowerOn()给相机上电
3.调用Observer的PowerOnComplete()函数通知系统上电完成
void CImageCapturerEngine::PowerOnComplete(TInt aError)
{
TInt err = aError;
if(aError == KErrNone)
{
TCameraInfo info;
iCamera->CameraInfo(info);
if ((info.iOptionsSupported&TCameraInfo::EContrastSupported)!=0)
{
TRAP(err, iCamera->SetContrastL(CCamera::EContrastAuto));
}

TRAP(err,StartViewFinderL());
if(err==KErrNone)
{
TRAP(err,PrepareImageCaptureL(KDefaultImageFormat));
}
}
if(err!=KErrNone)
{
iObserver.OnError(aError);
}
}
4.设置对比度，预览图像
void CImageCapturerEngine::ViewFinderFrameReady(CFbsBitmap& aFrame)
{
iObserver.OnFrame(aFrame);
}

5.准备捕捉图像
void CImageCapturerEngine::ImageReady(CFbsBitmap* aBitmap,HBufC8* /*aData*/,TInt aError)
{
if(aError == KErrNone)
{
iObserver.OnImage(aBitmap);
}
else
{
iObserver.OnError(aError);
}
}

6.重要的函数：开始预览图像和停止预览
void CImageCapturerEngine::StartViewFinderL()
{
TSize imageSize(KDefaultImageWidth,KDefaultImageHeight);

if(iCamera->ViewFinderActive())
{
// iObserver.OnError(KErrAlreadyActive)
}
else
{
iCamera->StartViewFinderBitmapsL(imageSize);
}
if(!iCamera->ViewFinderActive())
{
// iObserver.OnError(KErrNotActivated);
}
}

void CImageCapturerEngine::StopViewFinder()
{
iCamera->StopViewFinder();
}

7.捕捉图像
void CImageCapturerEngine::CaptureImage()
{
iCamera->CaptureImage();
}

补充：
（1）iCamera->SetContrastL(CCamera::EContrastAuto));
EContrastAuto-自动设置
还可以设置-100到100之间的值