Convert from HBITMAP to IWICBitmap

Question

I'm trying to convert an HBITMAP to an IWICBitmap, and I'm having quite a bit of trouble. I found the function:

CreateBitmapFromHBITMAP();

but I can't get it to work. Here is how I am using it:

void camera_avtcam_ex_t::GrabAsyncFrame(ULONG frameId, IWICImagingFactory* pWicFactory, IWICBitmap** outputBitmap, bool* pAbort )
{

        QueueCamFrame();
        HBITMAP transferbitmap;
        GetFeatureAndRunAcquisitionStart(transferbitmap); //returns transferbitmap 
                                                          //as a valid HBITMAP
       //This HBITMAP works, I can save it to a file and/or print 
       //it to the screen and the image is displayed properly

        pWicFactory->CreateBitmapFromHBITMAP(transferbitmap, NULL, WICBitmapUseAlpha, outputBitmap);

}

Executing that last line of code in the function causes an access violation error.

Right before this GrabAsyncFrame() function is called, I create the parameters it needs like this:

        ULONG frameId = 0;
        IWICImagingFactory* pWicFactory = NULL;
        IWICBitmap** outputBitmap = new IWICBitmap*;
        bool* pAbort = NULL;

        theCamera.GrabAsyncFrame(frameId, pWicFactory, outputBitmap, pAbort);

I'm kind of suspect to setting pWicFactory to NULL, and then using it soon after. But I couldn't figure out any other way to initialize the IWICImagingFactory objects.

So my question is: New question is posted below.

EDIT: If I try using new to initialize pWicFactory, I get a message saying

Error: object of abstract class type "IWICImagingFactory" is not allowed.

EDIT2:

After confirming that setting pWicFactory to NULL was the problem, I now need to know how to properly initialize an IWICImagingFactory object pointer. This is what I'm working with now:

            ULONG frameId = 0;
            IWICImagingFactory* pWicFactory = NULL;
/*new code*/CoCreateInstance(CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pWicFactory));
            IWICBitmap** outputBitmap = new IWICBitmap*;
            bool* pAbort = NULL;
            theCamera.GrabAsyncFrame(frameId, pWicFactory, outputBitmap, pAbort);

Question: How do I properly initialize an IWICImagingFactory object pointer?

So the CoCreateInstance call is failing? Assign the return value to an HRESULT variable and look at its description in the debugger, then edit the question with that description. — user1610015, Mar 15 '13 at 14:05
Aha. I just needed to call `CoInitialize(NULL)` before using `CoCreateInstance()`. Works fine now :) — xcdemon05, Mar 15 '13 at 14:30

score 1 · Accepted Answer · answered Mar 15 '13 at 13:12

1

This declaration

IWICImagingFactory* pWicFactory = NULL;

is the culprit.

You're passing a NULL pointer to the function, which you then try to use, causing the error.

answered Mar 15 '13 at 13:12

Some programmer dude

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Okay as I stated in my question I had a feeling that was the problem, but to answer my question, what would be a better way of initializing it? Using `new` is the only other method I can think of, but I can't do that. – xcdemon05 Mar 15 '13 at 13:14
Try - CoCreateInstance(CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pIWICFactory)); – Roger Rowland Mar 15 '13 at 13:16
@xcdemon05 So your question isn't really about the error you have, but how to create this object? – Some programmer dude Mar 15 '13 at 13:18
@JoachimPileborg My question was why isn't this working. I had a feeling initializing to NULL was part of the problem, but I wasn't sure. Knowing this now, my followup question is how to create the object. – xcdemon05 Mar 15 '13 at 13:21
@roger_rowland After that line of code, my debugger still says that the value of pWicFactory is 0x0000000000000000 – xcdemon05 Mar 15 '13 at 13:24
If you are on Windows 7 or 8 - try 'CLSID_WICImagingFactory1' instead of 'CLSID_WICImagingFactory'. – Roger Rowland Mar 15 '13 at 13:25
@roger_rowland It's not recognized by the compiler :( – xcdemon05 Mar 15 '13 at 13:27
What OS are you on? WIC needs minimum XP with SP2. – Roger Rowland Mar 15 '13 at 13:29
1

Ok, I suggest that you edit your original question to show the latest code and then we can see what you're doing now. – Roger Rowland Mar 15 '13 at 13:30
Before you can use `CoCreateInstance()` you need to call `CoInitialize(NULL)` (or the later `CoInitializeEx` version). Then before you exit the program, call `CoUninitialize()`. Beware that if you use `ComPtr` to hold your `IWICImagingFactory` pointer, you need to `Reset()` before calling CoUninitialize. – d7samurai Apr 20 '14 at 15:18

d7samurai · Answer 2 · 2014-04-20T15:44:14.927

Aside from the nullpointer issue, you probably forgot to call CoInitialize first:

IWICImagingFactory* Factory;

...

CoInitializeEx(NULL, COINIT_MULTITHREADED); // do this during program init / before CoCreateInstance

CoCreateInstance(CLSID_WICImagingFactory, nullptr, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&Factory));

// use factory..

CoUninitialize(); // do this before program exit.

Note that if you keep your factory pointer in a ComPtr (which I recommend), you need to release the factory interface before uninitializing. In that case you should do:

ComPtr<IWICImagingFactory> Factory;

...

CoInitializeEx(NULL, COINIT_MULTITHREADED); // do this during program init / before CoCreateInstance

CoCreateInstance(CLSID_WICImagingFactory, nullptr, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&Factory));

// use factory..

Factory.Reset(); // do this before CoUninitialize

CoUninitialize(); // do this before program exit.

Also be sure to check the HRESULT returned by CoInitialize and CoCreateInstance (omitted here for brevity)...

EDIT: I now see in a comment that this was indeed your problem. I'll leave my answer though, in case others are as sloppy-sighted as me..

Convert from HBITMAP to IWICBitmap

2 Answers2