F项目进行到最终界面设计阶段了。在把320x240分辨率的摄像头图像放到640x480的视窗之后,解析度很低,决定添加让用户选择分辨率的界面。
先看了DirectX自带的AmCap Sample,在里面找到这样一段代码:
IAMStreamConfig *pSC;
hr = gcap.pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Interleaved, gcap.pVCap,
IID_IAMStreamConfig, (void **)&pSC);
if(hr != NOERROR)
hr = gcap.pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Video, gcap.pVCap,
IID_IAMStreamConfig, (void **)&pSC);
ISpecifyPropertyPages *pSpec;
CAUUID cauuid;
hr = pSC->QueryInterface(IID_ISpecifyPropertyPages,
(void **)&pSpec);
if(hr == S_OK)
{
hr = pSpec->GetPages(&cauuid);
hr = OleCreatePropertyFrame(ghwndApp, 30, 30, NULL, 1,
(IUnknown **)&pSC, cauuid.cElems,
(GUID *)cauuid.pElems, 0, 0, NULL);
// !!! What if changing output formats couldn't reconnect
// and the graph is broken? Shouldn't be possible
if(gcap.pVSC)
{
AM_MEDIA_TYPE *pmt;
// get format being used NOW
hr = gcap.pVSC->GetFormat(&pmt);
// DV capture does not use a VIDEOINFOHEADER
if(hr == NOERROR)
{
if(pmt->formattype == FORMAT_VideoInfo)
{
// resize our window to the new capture size
ResizeWindow(HEADER(pmt->pbFormat)->biWidth,
abs(HEADER(pmt->pbFormat)->biHeight));
}
DeleteMediaType(pmt);
}
}
CoTaskMemFree(cauuid.pElems);
pSpec->Release();
}
pSC->Release();
hr = gcap.pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Interleaved, gcap.pVCap,
IID_IAMStreamConfig, (void **)&pSC);
if(hr != NOERROR)
hr = gcap.pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Video, gcap.pVCap,
IID_IAMStreamConfig, (void **)&pSC);
ISpecifyPropertyPages *pSpec;
CAUUID cauuid;
hr = pSC->QueryInterface(IID_ISpecifyPropertyPages,
(void **)&pSpec);
if(hr == S_OK)
{
hr = pSpec->GetPages(&cauuid);
hr = OleCreatePropertyFrame(ghwndApp, 30, 30, NULL, 1,
(IUnknown **)&pSC, cauuid.cElems,
(GUID *)cauuid.pElems, 0, 0, NULL);
// !!! What if changing output formats couldn't reconnect
// and the graph is broken? Shouldn't be possible
if(gcap.pVSC)
{
AM_MEDIA_TYPE *pmt;
// get format being used NOW
hr = gcap.pVSC->GetFormat(&pmt);
// DV capture does not use a VIDEOINFOHEADER
if(hr == NOERROR)
{
if(pmt->formattype == FORMAT_VideoInfo)
{
// resize our window to the new capture size
ResizeWindow(HEADER(pmt->pbFormat)->biWidth,
abs(HEADER(pmt->pbFormat)->biHeight));
}
DeleteMediaType(pmt);
}
}
CoTaskMemFree(cauuid.pElems);
pSpec->Release();
}
pSC->Release();
先是用ICaptureGraphBuilder2::FindInterface将Capture Filter的属性读到IAMStreamConfig中,再通过QueryInterface将IAMStreamConfig与ISpecifyPropertyPages关联起来,然后利用OLE自带的OleCreatePropertyFrame来生成属性页面,供用户选取。
后面的代码是根据读到的信息调整UI,并作些结束处理。
以上实地一种方法,但是每次都要选择才能达到640x480的分辨率,感觉很不人性化,假如用户希望定义默认值为640x480而不是320x240,那就需要别的方法了。
在DirectX的文档中看到这样一篇文章:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnanchor/html/anch_directx.asp
先把Capture Filter的属性读到IAMStreamConfig:
IAMStreamConfig *pConfig = NULL;
hr = pBuild->FindInterface(
&PIN_CATEGORY_PREVIEW, // Preview pin.
0, // Any media type.
pCap, // Pointer to the capture filter.
IID_IAMStreamConfig, (void**)&pConfig);
hr = pBuild->FindInterface(
&PIN_CATEGORY_PREVIEW, // Preview pin.
0, // Any media type.
pCap, // Pointer to the capture filter.
IID_IAMStreamConfig, (void**)&pConfig);
然后将属性中的每个AM_MEDIA_TYPE读出,处理。
int iCount = 0, iSize = 0;
hr = pConfig->GetNumberOfCapabilities(&iCount, &iSize);
// Check the size to make sure we pass in the correct structure.
if (iSize == sizeof(VIDEO_STREAM_CONFIG_CAPS)
{
// Use the video capabilities structure.
for (int iFormat = 0; iFormat < iCount; iFormat++)
{
VIDEO_STREAM_CONFIG_CAPS scc;
AM_MEDIA_TYPE *pmtConfig;
hr = pConfig->GetStreamCaps(iFormat, &pmtConfig, (BYTE*)&scc);
if (SUCCEEDED(hr))
{
/* Examine the format, and possibly use it. */
// Delete the media type when you are done.
DeleteMediaType(pmtConfig);
}
}
hr = pConfig->GetNumberOfCapabilities(&iCount, &iSize);
// Check the size to make sure we pass in the correct structure.
if (iSize == sizeof(VIDEO_STREAM_CONFIG_CAPS)
{
// Use the video capabilities structure.
for (int iFormat = 0; iFormat < iCount; iFormat++)
{
VIDEO_STREAM_CONFIG_CAPS scc;
AM_MEDIA_TYPE *pmtConfig;
hr = pConfig->GetStreamCaps(iFormat, &pmtConfig, (BYTE*)&scc);
if (SUCCEEDED(hr))
{
/* Examine the format, and possibly use it. */
// Delete the media type when you are done.
DeleteMediaType(pmtConfig);
}
}
在这里我要做的是,在众多支持的AM_MEDIA_TYPE中挑选一种合适的,作为默认选项。
if ((pmtConfig->majortype == MEDIATYPE_Video) &&
(pmtConfig->subtype == MEDIASUBTYPE_RGB24) &&
(pmtConfig->formattype == FORMAT_VideoInfo) &&
(pmtConfig->cbFormat >= sizeof (VIDEOINFOHEADER)) &&
(pmtConfig->pbFormat != NULL))
{
VIDEOINFOHEADER *pVih = (VIDEOINFOHEADER*)pmtConfig->pbFormat;
// pVih contains the detailed format information.
LONG lWidth = pVih->bmiHeader.biWidth;
LONG lHeight = pVih->bmiHeader.biHeight;
if(lWidth == 640)
pSC->SetFormat(pmtConfig);
}
(pmtConfig->subtype == MEDIASUBTYPE_RGB24) &&
(pmtConfig->formattype == FORMAT_VideoInfo) &&
(pmtConfig->cbFormat >= sizeof (VIDEOINFOHEADER)) &&
(pmtConfig->pbFormat != NULL))
{
VIDEOINFOHEADER *pVih = (VIDEOINFOHEADER*)pmtConfig->pbFormat;
// pVih contains the detailed format information.
LONG lWidth = pVih->bmiHeader.biWidth;
LONG lHeight = pVih->bmiHeader.biHeight;
if(lWidth == 640)
pSC->SetFormat(pmtConfig);
}
这样,初始模式就设在了640x480上,但是如果设备不支持640,就不会更改了。
第二种方法也成功了。