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POGet iplImage or Mat from directshow to opencv
 

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  1. POGet iplImage or Mat from directshow to opencv
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    <p>I had to change to directshow for my eyetracking software due to the difficulties to change resolution of the camera when using c++ and opencv. </p> <p>Directshow is new to me and it is kind of hard to understand everything. But I found this nice example that works perfectly for capturing &amp; viewing the web cam. </p> <p><a href="http://www.codeproject.com/Articles/12869/Real-time-video-image-processing-frame-grabber-usi" rel="nofollow">http://www.codeproject.com/Articles/12869/Real-time-video-image-processing-frame-grabber-usi</a></p> <p>I am using the version that not requires directShow SDK. (But it is still directshow that is used in the example, right??)</p> <pre><code>#include &lt;windows.h&gt; #include &lt;dshow.h&gt; #pragma comment(lib,"Strmiids.lib") #define DsHook(a,b,c) if (!c##_) { INT_PTR* p=b+*(INT_PTR**)a; VirtualProtect(&amp;c##_,4,PAGE_EXECUTE_READWRITE,&amp;no);\ *(INT_PTR*)&amp;c##_=*p; VirtualProtect(p, 4,PAGE_EXECUTE_READWRITE,&amp;no); *p=(INT_PTR)c; } // Here you get image video data in buf / len. Process it before calling Receive_ because renderer dealocates it. HRESULT ( __stdcall * Receive_ ) ( void* inst, IMediaSample *smp ) ; HRESULT __stdcall Receive ( void* inst, IMediaSample *smp ) { BYTE* buf; smp-&gt;GetPointer(&amp;buf); DWORD len = smp-&gt;GetActualDataLength(); HRESULT ret = Receive_ ( inst, smp ); return ret; } int WINAPI WinMain(HINSTANCE inst,HINSTANCE prev,LPSTR cmd,int show){ HRESULT hr = CoInitialize(0); MSG msg={0}; DWORD no; IGraphBuilder* graph= 0; hr = CoCreateInstance( CLSID_FilterGraph, 0, CLSCTX_INPROC,IID_IGraphBuilder, (void **)&amp;graph ); IMediaControl* ctrl = 0; hr = graph-&gt;QueryInterface( IID_IMediaControl, (void **)&amp;ctrl ); ICreateDevEnum* devs = 0; hr = CoCreateInstance (CLSID_SystemDeviceEnum, 0, CLSCTX_INPROC, IID_ICreateDevEnum, (void **) &amp;devs); IEnumMoniker* cams = 0; hr = devs?devs-&gt;CreateClassEnumerator (CLSID_VideoInputDeviceCategory, &amp;cams, 0):0; IMoniker* mon = 0; hr = cams-&gt;Next (1,&amp;mon,0); // get first found capture device (webcam?) IBaseFilter* cam = 0; hr = mon-&gt;BindToObject(0,0,IID_IBaseFilter, (void**)&amp;cam); hr = graph-&gt;AddFilter(cam, L"Capture Source"); // add web cam to graph as source IEnumPins* pins = 0; hr = cam?cam-&gt;EnumPins(&amp;pins):0; // we need output pin to autogenerate rest of the graph IPin* pin = 0; hr = pins?pins-&gt;Next(1,&amp;pin, 0):0; // via graph-&gt;Render hr = graph-&gt;Render(pin); // graph builder now builds whole filter chain including MJPG decompression on some webcams IEnumFilters* fil = 0; hr = graph-&gt;EnumFilters(&amp;fil); // from all newly added filters IBaseFilter* rnd = 0; hr = fil-&gt;Next(1,&amp;rnd,0); // we find last one (renderer) hr = rnd-&gt;EnumPins(&amp;pins); // because data we are intersted in are pumped to renderers input pin hr = pins-&gt;Next(1,&amp;pin, 0); // via Receive member of IMemInputPin interface IMemInputPin* mem = 0; hr = pin-&gt;QueryInterface(IID_IMemInputPin,(void**)&amp;mem); DsHook(mem,6,Receive); // so we redirect it to our own proc to grab image data hr = ctrl-&gt;Run(); while ( GetMessage( &amp;msg, 0, 0, 0 ) ) { TranslateMessage( &amp;msg ); DispatchMessage( &amp;msg ); } }; </code></pre> <p>The method HRESULT Receive is called for every new frame from the cam. the the comments says that buf contains the data. But I have 3 problems/questions.</p> <ol> <li><p>I cant include the opencv lib. I create a new project in visual studio, and add the same property sheets as I always include. the only difference from earlier projects is that I Now create a totaly empty project, earlier I created a win32 application. How to add opencv into the directshow project?</p></li> <li><p>The example above. from buf. which is a pointer to the data. How do I get that into iplImage/Mat for the opencv calc?</p></li> <li><p>Is there a way to not show the images from the webcam (I only need to perform some algorithms on the frames, I guess removing the window with the results might give me more power for the analyse algorithms?!)</p></li> </ol> <p>Thanks!</p>
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    1. COThe snippet you took as a sample is terrible: use of raw pointers, hook instead of normal API, no stop/termination code. You will quickly get nowhere with this.
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    2. COThanks for your comment. yeah I have read that this example is terrible. But the thing is that this is the only example that I found that I in some way understand and that is working. This COM stuff & directshow is totally new for me and I think it is really hard to understand. If you know any example with better code (that is a bit easier to understand) please give me a link.
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    3. COBut I really need to learn, and to learn to build GOOD code. If there is anyone that have nice examplecode please let me know! I've been working with directshow for a couple of days only and need to learn.
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