How to detect numbers/digits via builtin OcrEngine class - windows

Question

I have troubles detecting digits/numbers in an image with the Windows UWP OCR-Engine from C++/CX.
I need to detect the number in the following Image
I tried it by using the builtin method for Windows 10 UWP: OcrEngine with the following code:
...
cv::Mat croppedImage = imread("digit.png");
WriteableBitmap^ bit1 = ref new WriteableBitmap(croppedImage.cols, croppedImage.rows);
SoftwareBitmap^ bit2 = bit2->CreateCopyFromBuffer(bit1->PixelBuffer, BitmapPixelFormat::Bgra8, bit1->PixelWidth, bit1->PixelHeight);
Windows::Globalization::Language^ l = ref new Windows::Globalization::Language("de");
OcrEngine^ ocrEngine = OcrEngine::TryCreateFromLanguage(l);
IAsyncOperation<OcrResult^>^ ao = ocrEngine->RecognizeAsync(bit2);
task_completion_event<Platform::String^> purchaseCompleted;
auto deviceEnumTask = create_task(ao);
deviceEnumTask.then([this](OcrResult^ result)
{
App1::MainPage::findNumber(result->Text);
});
...
void App1::MainPage::findNumber(Platform::String^ text)
{
//Do something with String
}
My Problem is now, that the inserted string in findNumber is always null. I tried with different pictures as input but always the same result: NULL.
Is there an easier way to get the digits in this images in C++/CX?
What could be the problem? Converting the image?

Answer 1

The problem was the conversion of the WriteableBitmap to a SoftwareBitmap WriteableBitmap^ bit1 = ref new WriteableBitmap(croppedImage.cols, croppedImage.rows);
// Get access to the pixels
IBuffer^ buffer = bit1->PixelBuffer;
unsigned char* dstPixels;
// Obtain IBufferByteAccess
ComPtr<IBufferByteAccess> pBufferByteAccess;
ComPtr<IInspectable> pBuffer((IInspectable*)buffer);
pBuffer.As(&pBufferByteAccess);
// Get pointer to pixel bytes
pBufferByteAccess->Buffer(&dstPixels);
memcpy(dstPixels, croppedImage.data, croppedImage.step.buf[1] * croppedImage.cols*croppedImage.rows);
SoftwareBitmap^ bit2= ref new SoftwareBitmap(BitmapPixelFormat::Bgra8, croppedImage.cols, croppedImage.rows);
//SoftwareBitmap^ bit2 =
bit2->CopyFromBuffer(bit1->PixelBuffer);