Function to convert cv::Mat to Win32 HBITMAP aka BMP; function to paste HBITMAP to Windows clipboard.

ConvertCVMatToWin32BMP.cpp

#include <cassert>
#include "opencv2/opencv.hpp"


auto ConvertCVMatToBMP (cv::Mat frame) -> HBITMAP
{      
    auto convertOpenCVBitDepthToBits = [](const int32_t value)
    {
        auto regular = 0u;
    
        switch (value)
        {
        case CV_8U:
        case CV_8S:
            regular = 8u;
            break;

        case CV_16U:
        case CV_16S:
            regular = 16u;
            break;

        case CV_32S:
        case CV_32F:
            regular = 32u;
            break;

        case CV_64F:
            regular = 64u;
            break;

        default:
            regular = 0u;
            break;
        }

        return regular;
    };

    auto imageSize = frame.size();
    assert(imageSize.width && "invalid size provided by frame");
    assert(imageSize.height && "invalid size provided by frame");
    
    if (imageSize.width && imageSize.height)
    {
        auto headerInfo = BITMAPINFOHEADER{};
        ZeroMemory(&headerInfo, sizeof(headerInfo));
        
        headerInfo.biSize     = sizeof(headerInfo);
        headerInfo.biWidth    = imageSize.width;
        headerInfo.biHeight   = -(imageSize.height); // negative otherwise it will be upsidedown
        headerInfo.biPlanes   = 1;// must be set to 1 as per documentation frame.channels();
        
        const auto bits       = convertOpenCVBitDepthToBits( frame.depth() );
        headerInfo.biBitCount = frame.channels() * bits;

        auto bitmapInfo = BITMAPINFO{};
        ZeroMemory(&bitmapInfo, sizeof(bitmapInfo));
        
        bitmapInfo.bmiHeader              = headerInfo;
        bitmapInfo.bmiColors->rgbBlue     = 0;
        bitmapInfo.bmiColors->rgbGreen    = 0;
        bitmapInfo.bmiColors->rgbRed      = 0;
        bitmapInfo.bmiColors->rgbReserved = 0;
        
        auto dc  = GetDC(nullptr);
        assert(dc != nullptr && "Failure to get DC");
        auto bmp = CreateDIBitmap(dc,
                                  &headerInfo,
                                  CBM_INIT,
                                  frame.data,
                                  &bitmapInfo,
                                  DIB_RGB_COLORS);
        assert(bmp != nullptr && "Failure creating bitmap from captured frame");
        
        return bmp;
    }
    else
    {
    	return nullptr;
    }
}

auto PasteBMPToClipboard(void* bmp) -> bool
{
	assert(bmp != nullptr && "You need a bmp for this function to work");

	if (OpenClipboard(NULL) && bmp != nullptr)
    {
        EmptyClipboard();
        SetClipboardData(CF_BITMAP, bmp);
        CloseClipboard();
        return true;
    }
    else
    {
        return false;
    }	
}


int main(int argc, char const *argv[])
{
	auto emptyFrame = cv::Mat{};
	auto bmp = ConvertCVMatToBMP(emptyFrame);

	if (bmp)
	{
		auto pasteResult = PasteBMPToClipboard(bmp);
		(void)pasteResult; // examine result at your convenience
		DeleteObject(bmp);
	}

	return 0;
}

@AhiyaHiya

the image is Oblique,

i had no idea to modify the bitmap 's stride.

how to fix it?

@AhiyaHiya

the problem can be happened that if the mat ' s cols is Not a multiple of 4

so when i resize the mat

	resize(frame, frame, Size(frame.cols / 4 * 4, frame.rows));

it correctly work!

and then i want you to Explain what is the real inner of this problem.

and finish to find a way keep the orginal size of the mat.

@AhiyaHiya
when i translate gray mat into bitmap,
it become all blcak?
it happens always, you can check it!
please fix it!!!

I'm not keen on your coding style, but after a cosmetic cleanup, this example works just great.
The only thing I would suggest is that you release the device context using...

ReleaseDC(nullptr,dc);

The documentation is clear. Without that call you have a GDI handle leak.
Thanks for the timesaver.

auto dc = GetDC(nullptr); I get error for this. 'too many arguments in function call'
how come?
But i solved it when i use :
CDC* p = GetDC();
HDC dc = p->m_hDC;

Then i tried to display the HBITMAP using the following code but its not showing anything. Do you know why? thanks.

m_pic.GetClientRect(&rectStaticClient);
rectStaticClient.NormalizeRect();
m_size.cx = rectStaticClient.Size().cx;
m_size.cy = rectStaticClient.Size().cy;
m_size.cx = rectStaticClient.Width(); // zero based
m_size.cy = rectStaticClient.Height(); // zero based

	// Convert to screen coordinates using static as base,
	// then to DIALOG (instead of static) client coords 
	// using dialog as base
	m_pic.ClientToScreen(&rectStaticClient);
	ScreenToClient(&rectStaticClient);

	m_pt.x = rectStaticClient.left;
	m_pt.y = rectStaticClient.top;
	GetObject(m_hBmpNew, sizeof(BITMAP), &m_bmInfo);
	VERIFY(m_hBmpOld = (HBITMAP)SelectObject(m_dcMem, m_hBmpNew));
	offsetx = m_pt.x;
	offsety = m_pt.y;
	InvalidateRect(&rectStaticClient);