在Windows（C ++）中从USB相机拍摄高分辨率照片

Question

I am developing an C++ application which should use an USB camera to capture high resolution photos. It should have same behavior as the Camera application in Windows 10. I am trying to use DirectShow for doing it. Now I am only able to take high resolution photo which is delayed or take a photo in time but low resolution. Also I am very confused from MS documentation, lot of things are deprecated and nowhere mentioned what replaces them. I'll describe my hopeless steps awaiting there will be somebody who could be able to show me a way.

Let's start from beginning...

Knowing nothing about video capturing in Window I started by searching suitable library. After some googling I found there are four main libraries for capturing video in Windows.

1. Video for Windows
2. DirectShow
3. Windows Media Foundation
4. OpenCV

Let's observe:

1. Video for Windows
   This library is unfortunately marked as deprecated but it seems it still works. I have written "unfortunately", because I think this is the only which is easy to use. There are only a few lines of code needed for seeing video from camera. The only think I miss here is a "TakePhoto" function. You can use VFW for capture a video or single frames to an avi file. Or am I missing something?

2. DirectShow
   This is much more complicated library. You need hundreds of lines of code to see a video preview. But you can obtain this code on MS Docs. Ok, now I have a video preview and I need only to take a photo. One would expect this should be just one function call. But where is the function? I did not find it.

You can simply use GetCurrentImage from IVMRWindowlessControl but this takes only one frame from preview with low resolution. If you set a higher resolution for preview the video is not fluent.

Best approach I could achieve is from an article called "Capturing an Image From a Still Image Pin" available here https://docs.microsoft.com/en-us/windows/desktop/directshow/capturing-an-image-from-a-still-image-pin . When I had found this site I thought I won and my task was almost finished. But it wasn't.

The first advice which the article gives you is not to use it: "The recommended way to get still images from the device is to use the Windows Image Acquisition (WIA) APIs. For more information, see "Windows Image Acquisition" in the Platform SDK documentation. However, you can also use DirectShow to capture an image." I tried to explore the WIA. But this stopped to work on Vista. I continued to study the article.
Everything seems to be clear but you need to implement your class which inherits ISampleGrabberCB marked as deprecated here https://docs.microsoft.com/en-us/windows/desktop/directshow/isamplegrabbercb . Why???? Where to find some alternative?
I found an acceptable solution here https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/2ab5c212-5824-419d-b5d9-7f5db82f57cd/qedith-missing-in-current-windows-sdk-v70?forum=windowsdirectshowdevelopment . You need to add header file from elder SDK. (BTW This is an advice almost ten years old.) After I compiled the application with this header I was able to read high resolution picture but I need to wait a few seconds which is unacceptable. I know the problem is not in camera, because in the it works in the Camera application. Furthermore the image is obtained in function SampleCB instead of BufferCB and is in some strange format. I can save it as jpg but it is not compressed enough.

3. Windows Media Foundation
   I think MS doesn't like programmers and that's why it released WMF. I understand nothing. I found this tutorial https://www.dreamincode.net/forums/topic/347938-a-new-webcam-api-tutorial-in-c-for-windows/ . It works but it only stores one frame from preview and this is not what I want.
   Next I explored some WMF interfaces on MS Docs. IMFCapturePhotoSink interface should do the stuff. But how implement it. The documentation is useless.

4. OpenCV
   During my research I found also this library. But again I'm not able to take a high resolution photo. It only stores one frame from preview.

Could someone tell me what should I focus on? I believe it cannot be so difficult. There are tens and hundreds of applications for webcams. How could other programmers implement them? What's wrong with me? I'd like to find an easy way to implement an easy task. Thank a lot for any help.

Answer 1

You question is not related to the topic - the question must be related to the code - but I faced with the similar problem many years ago and I had found solution:

DirectShow is declared as deprecated for Windows 10 and it has problem with supporting of the USB web cam. In Windows 10 there is USB Video Class which is supported only by Media Foundation.

So, I have wrote a simple C++ wrapper around Media Foundation code which simplify getting of the raw images Capturing Video from Web-camera on Windows 7 and 8 by using Media Foundation

Also, there is project CaptureManager SDK - it is DLL COM component with the simple interfaces, huge functionality and with many demo programs on C++, Python, C#, Java.

Answer 2

Thanks to Evgeny.

Recapitulation:

1. Download the CaptureEngine video capture sample

2. Edit CaptureManager::TakePhoto method. Add the code to find highest resolution media type just before CreatePhotoMediaType(pMediaType, &pMediaType2); line

Extra code for setup the photo stream to highest resolution:

DWORD dwMediaTypeIndex = 0;
UINT32 maxSize = 0;
DWORD maxSizeIndex = 0;
while (1) {
    IMFMediaType* pMediaType = NULL;
    hr = pSource->GetAvailableDeviceMediaType((DWORD)MF_CAPTURE_ENGINE_PREFERRED_SOURCE_STREAM_FOR_PHOTO, dwMediaTypeIndex, &pMediaType);
    if (hr == MF_E_NO_MORE_TYPES)
        break;

    UINT32 w, h;
    MFGetAttributeSize(pMediaType, MF_MT_FRAME_SIZE, &w, &h);
    UINT32 size = w * h;
    if (size > maxSize) {
        maxSize = size;
        maxSizeIndex = dwMediaTypeIndex;
    }
    SafeRelease(&pMediaType);
    dwMediaTypeIndex++;
}

SafeRelease(&pMediaType);
pSource->GetAvailableDeviceMediaType((DWORD)MF_CAPTURE_ENGINE_PREFERRED_SOURCE_STREAM_FOR_PHOTO, maxSizeIndex, &pMediaType);